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Pigeonhole v2.4.5 tarball reuploaded
by Aki Tuomi 28 Aug '26

28 Aug '26

Hi! Due to logistics mistake, the pigeonhole tarball was reuploaded now to include man pages that had dropped out by mistake. No code changes or git changes sneaked in. Sorry for the inconvenience. Aki

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Dovecot Security Advisory 3/2026
by Aki Tuomi 28 Aug '26

28 Aug '26

Hi! We're sharing our latest advisory with you and like to thank everyone who contributed in finding and solving those vulnerabilities. This advisory will also be published at https://documentation.open-xchange.com/dovecot/security/advisories/html/202… --- Classification: TLP:GREEN Internal reference: DOV-8476 Type: CWE-403 (Exposure of File Descriptor to Unintended Control Sphere ('File Descriptor Leak')) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2025-11-25 Solution date: 2026-08-26 Disclosure date: 2026-08-26 CVE: CVE-2026-33263 CVSS: 4.3 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L) Details: submission-login: Panic when mail_max_userip_connections is reached: Panic: epoll_ctl(del, 8) failed: Bad file descriptor. When mail_max_userip_connections is set (defaul t 10) and reached, submission-login can crash with epoll() panic caused by file descriptor handling issues. Risk: If running in high-security mode (default for community releases), only the new submission connection gets terminated. If running in high-performance mode (default for Pr o releases), all connections handled by the submission-login process will be terminated. The crashes can cause failure for user to send a message, or it can cause duplica te messages to be sent. If TLS is not used (in the backend server processing the submission), duplicate deliveries cannot happen, because the crash can only happen at AUT H stage. No publicly available exploits are known. Solution: Limit the number of connections handled by single submission-login process. This has a performance impact though. Update to non-vulnerable version. --- Internal reference: DOV-8874 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-03-11 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: ylwango613@yeswehack CVE: CVE-2026-33607 CVSS: 4.3 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L) Details: Dovecot IMAP LIST match_sub() Exponential Backtracking — CPU Denial of Service. An attacker that has valid credentials can use IMAP LIST command to consume CPU. Risk: This can cause degradation or denial of service for IMAP. No publicly available exploits are known. Solution: Monitor system for abnormal CPU usage and kill the offending process and lock account. Alternatively install fixed version. --- Internal reference: DOV-8884 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-03-13 Solution date: 2026-08-26 Disclosure date: 2026-08-26 CVE: CVE-2026-27852 CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) Details: DoS by sending mail with bad header. An attacker that can send mail to a user can craft a message whose headers contain a very large number of email addresses or MIME par ameters, which causes excessive memory usage when the message is later parsed. Risk: The message is still delivered, but reading it over IMAP can exhaust the memory limit of the process and terminate it, causing denial of service for the affected user. No publicly available exploits are known. Solution: Update to non-vulnerable version. --- Internal reference: DOV-8941 Type: CWE-93 (Improper Neutralization of CRLF Sequences ('CRLF Injection')) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-03-24 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: thanos_haruki@yeswehack CVE: CVE-2026-33606 CVSS: 4.8 (CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:N) Details: dsync: Mail content can cause dsync protocol injection. Mail content stored by a user can be crafted so that it is interpreted as dsync protocol commands when an administ rator later runs dsync with the stream protocol, for example during a migration. Risk: Injected commands can modify mailbox state on the destination during migration or replication, including internal mailbox attributes that a user should not be able to set directly. It can also cause dsync errors. No publicly available exploits are known. Solution: Avoid running dsync with the stream protocol on mailboxes with untrusted content. Update to non-vulnerable version. --- Internal reference: DOV-8947 Type: CWE-655 (Insufficient Psychological Acceptability) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-03-24 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: heckintosh@yeswehack CVE: CVE-2026-33604 CVSS: 5.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N) Details: SMTP Smuggling via Missing Dot-Stuffing After Bare Carriage Return. An attacker that can get Dovecot to relay a message, for example through Sieve redirect or submission relay, can use a crafted line ending in the message body to bypass the outbound protection that prevents message content from being interpreted as SMTP commands. Risk: A downstream mail server that hasn't yet fixed the SMTP smuggling vulnerability can be tricked into treating part of the message body as new SMTP commands, allowing injec tion of spoofed email. This is the same vulnerability class as CVE-2023-51764 and CVE-2023-51766. No publicly available exploits are known. Solution: Where you control the receiving mail servers, ensure they reject bare carriage returns in message data. Update to non-vulnerable version. --- Internal reference: DOV-8949 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-03-24 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: djvirus@yeswehack CVE: CVE-2026-40014 CVSS: 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H) Details: IMAP THREAD REFERENCES O(N²) CPU DoS via Crafted References Header (index-thread-links.c). An attacker that can send mail to a user can craft a message header that makes the IMAP THREAD command consume CPU disproportionate to the size of the message. Risk: When a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. No publicly available exploits are known. Solution: Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. --- Internal reference: DOV-8991 Type: CWE-124 (Buffer Underwrite ('Buffer Underflow')) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-02 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: ilyar@yeswehack CVE: CVE-2026-40013 CVSS: 4.3 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L) Details: pigeonhole: Stack Buffer Underflow in Pigeonhole ManageSieve CHECKSCRIPT/PUTSCRIPT. An attacker that has valid credentials can submit a Sieve script containing an extreme numeric literal, which causes an out-of-bounds write when the ManageSieve service compiles the script. Risk: This causes memory corruption and an observed crash of the ManageSieve process, resulting in denial of service for script management. This might be able to be used for re mote code execution. No publicly available exploits are known. Solution: Disable the ManageSieve service if users do not need remote Sieve script management. Update to non-vulnerable version. --- Internal reference: DOV-8994 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-02 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: ilyar@yeswehack CVE: CVE-2026-33605 CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) Details: managesieve-login: Pre-auth crash. An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating. Risk: If running in high-security mode (default for community releases), only the attacker's own connection is terminated. If running in high-performance mode (default for Pro releases), all connections handled by the same managesieve-login process are terminated. Repeating the attack can cause denial of service for Sieve script management. No publicly available exploits are known. Solution: Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version. --- Internal reference: DOV-9039 Type: CWE-89 (Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-08 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: tipsennn@yeswehack CVE: CVE-2026-40018 CVSS: 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N) Details: MySQL multi-byte escaping wrong. None Risk: None No publicly available exploits are known. Solution: None --- Internal reference: DOV-9041 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot CE core >=2.4.3 <2.4.5 First fixed revision: OX Dovecot CE core 2.4.5 Discovery date: 2026-04-08 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: ilyar@yeswehack CVE: CVE-2026-40019 CVSS: 5.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H) Details: v2.4.3 regression: managesieve-login pre-auth infinite loop. An unauthenticated attacker can send a truncated quoted argument to the ManageSieve login process, which make s it spin in an infinite loop consuming CPU. Risk: This can cause degradation or denial of service for Sieve script management, and repeated connections can consume all available CPU on the server. No publicly available e xploits are known. Solution: Monitor system for abnormal CPU usage and kill the offending process. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable vers ion. --- Internal reference: DOV-9046 Type: CWE-125 (Out-of-bounds Read) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-08 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: tipsennn@yeswehack CVE: CVE-2026-40015 CVSS: 4.3 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L) Details: imap-hibernate can be crashed. An attacker that has valid credentials can open many connections to the imap-hibernate service and send invalid commands, which can intermi ttently cause an out-of-bounds read and crash the process. Risk: The crash interrupts hibernated IMAP sessions handled by the affected process, which can cause degradation of service for IMAP. No publicly available exploits are known. Solution: Disable IMAP hibernation. Update to non-vulnerable version. --- Internal reference: DOV-9047 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-08 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: djvirus@yeswehack CVE: CVE-2026-40017 CVSS: 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H) Details: IMAP THREAD O(M³) CPU DoS via CRC32 Hash Collision in strmap (mail-index-strmap.c / hash2.c). An attacker that can send mail to a user can craft a message header whose va lues are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issu e from CVE-2026-40014 and is not addressed by that fix. Risk: Whenever a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. No publicly available exploits are known . Solution: Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. --- Internal reference: DOV-9066 Type: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-12 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: ilhamaf@yeswehack CVE: CVE-2026-40203 CVSS: 3.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N) Details: IMAP Compression Can Reveal Whether a Small Synced Email Body Matches Sender-Chosen Text. When IMAP compression is enabled, the same compression state is reused across re sponses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox. Risk: An attacker that can send mail to a user and can also observe the sizes of that user's IMAP traffic can confirm whether the body of a small message matches a guessed text . Recovery of arbitrary unknown content was not demonstrated, but the attack can disclose whether a secret-like message body matches a candidate. No publicly available ex ploits are known. Solution: Disable IMAP compression. Update to non-vulnerable version. --- Internal reference: DOV-9070 Type: CWE-416 (Use After Free) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-14 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: ilyar@yeswehack CVE: CVE-2026-42007 CVSS: 9.1 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H) Details: Sieve editheader RCE. An attacker that has valid credentials can use a Sieve script with the editheader extension to trigger a use-after-free in the mail editing code, an d to write memory contents beyond the intended buffer into the delivered mail. Risk: This causes memory leak and opportunity to do memory corruption during mail delivery, which can crash the delivery process and may allow execution of arbitrary code in th e context of that process. No publicly available exploits are known. Solution: Disable the Sieve editheader extension. Update to non-vulnerable version. --- Internal reference: DOV-9099 Type: CWE-284 (Improper Access Control) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-22 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: ilhamaf@yeswehack CVE: CVE-2026-40204 CVSS: 3.1 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N) Details: acl: lda_mailbox_autocreate can bypass acl restrictions. None Risk: None No publicly available exploits are known. Solution: None --- Internal reference: DOV-9106 Type: CWE-287 (Improper Authentication) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.11.2 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.11.2 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-23 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: Noobosaurus@yeswehack CVE: CVE-2026-40205 CVSS: 5.9 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N) Details: OAuth2 passdb scope enforcement bypass via OR semantics in remote validation path. An attacker that holds an OAuth2 token granting only part of the required scopes can au thenticate, because when more than one scope is required in the configuration, the remote token validation paths accept a token that carries only one of them, while the l ocal token validation path correctly requires all of them. Risk: The configured authorization policy is not enforced, so a token that was granted only part of the required permissions is accepted where it should have been rejected. No publicly available exploits are known. Solution: Use local token validation where tokens can be validated locally. Update to non-vulnerable version. --- Internal reference: DOV-9109 Type: CWE-287 (Improper Authentication) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.4 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.4 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-23 Solution date: 2026-08-26 Disclosure date: 2026-08-26 CVE: CVE-2026-42008 CVSS: 4.3 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N) Details: XCLIENT FORWARD= bare token not namespaced, allows nopassword injection via trusted proxy. Forwarding information received from a host listed as a trusted proxy is not ke pt separate from Dovecot's own authentication fields, so a value sent by that host can be injected as an internal authentication field. Risk: Any host permitted to act as a trusted proxy can authenticate as any user without knowing that user's password. This affects deployments whose password database honours a field that permits authentication without a password. Deployments that do not configure trusted proxies are not affected. No publicly available exploits are known. Solution: Restrict the list of trusted proxy networks to hosts that are fully under your control. Update to non-vulnerable version. --- Internal reference: DOV-9142 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-27 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: ilhamaf@yeswehack CVE: CVE-2026-42395 CVSS: 4.3 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L) Details: Single NUL-Byte XCLIENT FORWARD Payload Crashes. A host listed as a trusted proxy can send forwarding information containing a NUL byte, which crashes the login process o n the following login attempt. Risk: The login process is terminated, which can cause degradation or denial of service for logins. Deployments that do not configure trusted proxies are not affected. No publi cly available exploits are known. Solution: Restrict the list of trusted proxy networks to hosts that are fully under your control. Update to non-vulnerable version. --- Internal reference: DOV-9148 Type: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-04-27 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: D4RKCYPH3R@yeswehack CVE: CVE-2026-42393 CVSS: 3.1 (CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N) Details: doveadm_password or api key length can still be leaked with timing comparisons. The comparison used for the doveadm password and API key is not fully timing safe and can reveal the length of the configured secret. Risk: An attacker with access to the same network as the doveadm service, able to make repeated requests and measure response timing accurately, can learn the length of the sec ret, which reduces the effort needed to guess it. The secret value itself is not disclosed. No publicly available exploits are known. Solution: Restrict network access to the doveadm service to trusted clients. Update to non-vulnerable version. --- Internal reference: DOV-9223 Type: CWE-1050 (Excessive Platform Resource Consumption within a Loop) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.15 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.15 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-05-05 Solution date: 2026-08-26 Disclosure date: 2026-08-26 CVE: CVE-2026-52681 CVSS: 3.1 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L) Details: Sieve resource usage tracking lost when active script changes. Sieve CPU resource usage is tracked in the compiled script, so an attacker that has valid credentials can r eset the accounting by repeatedly changing the active script. Compiled script files are also not removed when a script is deleted or renamed. Risk: The configured Sieve CPU limit can be bypassed, allowing sustained CPU consumption, and the leftover files increase disk consumption. Both can cause degradation of servic e for mail delivery. No publicly available exploits are known. Solution: Monitor system for abnormal CPU usage and disk consumption. Update to non-vulnerable version. --- Internal reference: DOV-9230 Type: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-05-06 Solution date: 2026-08-26 Disclosure date: 2026-08-26 Researcher credits: djvirus@yeswehack CVE: CVE-2026-42392 CVSS: 4.3 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N) Details: imap-urlauth leaks memory into user-visible error messages. An attacker that has valid credentials can send an invalid IMAP URLFETCH command, which causes uninitialized m emory to be included in the error response returned to the client. Risk: Process memory contents can be disclosed to the client, which may include sensitive data. No publicly available exploits are known. Solution: Disable the IMAP URLAUTH functionality. Update to non-vulnerable version. --- Internal reference: DOV-9309 Type: CWE-287 (Improper Authentication) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.13 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.13 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-05-28 Solution date: 2026-08-26 Disclosure date: 2026-08-26 CVE: CVE-2026-73208 CVSS: 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N) Details: auth: db-oauth2: aud claim used as fallback for missing scope claim. An attacker that holds a token intended for a different purpose can authenticate, because when an OAu th2 token response does not contain a scope claim, the audience claim is used in its place and checked against the configured required scopes. These are different concept s, and the audience claim does not describe what a token is allowed to do. Risk: A token that grants no relevant permissions can be accepted because its intended recipient value happens to match a configured scope name, granting access that should hav e been denied. It also hides an identity provider misconfiguration where scopes are not being issued at all. No publicly available exploits are known. Solution: Ensure the identity provider issues a scope claim for all tokens used with Dovecot, and that configured scope names do not match audience values. Update to non-vulnerable version. --- Internal reference: DOV-9401 Type: CWE-674 (Uncontrolled Recursion) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-06-10 Solution date: 2026-08-26 Disclosure date: 2026-08-26 CVE: CVE-2026-73209 CVSS: 6.5 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) Details: imap-login crash: Self-recursion on zero-output decompress chunks. An attacker that has valid credentials can send crafted compressed data that causes the affected proces s to exhaust its stack and crash. Risk: The affected process is terminated, which can cause degradation or denial of service for IMAP. No publicly available exploits are known. Solution: Update to non-vulnerable version. --- Internal reference: DOV-9529 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.0 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.0 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-07-04 Solution date: 2026-08-26 Disclosure date: 2026-08-26 CVE: CVE-2026-42391 CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) Details: imap: Pre-login memory/CPU growth with ID command. An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. Risk: The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. No publicly available exploits are known. Solution: Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. --- Internal reference: DOV-9530 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Affected versions: OX Dovecot Pro core >=2.3.11 <2.3.22.2, OX Dovecot Pro core >=3.0.0 <3.0.7, OX Dovecot Pro core >=3.1.0 <3.1.6, OX Dovecot CE core >=2.3.11 <2.4.5 First fixed revision: OX Dovecot Pro core 3.0.7, OX Dovecot Pro core 2.3.22.2, OX Dovecot Pro core 3.1.6, OX Dovecot CE core 2.4.5 Discovery date: 2026-07-04 Solution date: 2026-08-26 Disclosure date: 2026-08-26 CVE: CVE-2026-52687 CVSS: 6.5 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) Details: IMAP: COMPRESS ZSTD can cause excessive memory usage. An attacker that has valid credentials can select a compression algorithm for the IMAP connection whose decompressio n state requires a large amount of memory, and open several such connections. Risk: The memory limit of the process is reached with only a few connections, terminating the process and all connections it handles, which can cause degradation or denial of s ervice for IMAP. No publicly available exploits are known. Solution: Disable IMAP compression. Alternatively limit the number of connections handled by a single imap-login process, though this has a performance impact. Update to non-vulner able version.

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Dovecot and Pigeonhole v2.4.5 released
by Aki Tuomi 28 Aug '26

28 Aug '26

Hi! We are happy to publish version 2.4.5 of Dovecot and Pigeonhole. These contain CVEs, discovered by external researches. The majority of these have been discovered with help of automated code analysis tools like claude code security, which is why some of these are rather old, missed bugs. Distributions have changed - Jammy (Ubuntu 22.04) is no longer provided in repo.dovecot.org - Resolute Raccoon (Ubuntu 26.04) has been added to repo.dovecot.org No new dependencies have been added. Note that there are experimental features in 2.4, one is enabled with `--enable-experimental-mail-utf8`, and another with `--enable-experimental-imap4rev2`, and you also need to set mail_utf8_extensions=yes and imap4rev2_enabled=yes to enable them in config. https://dovecot.org/releases/2.4/dovecot-2.4.5.tar.gz https://dovecot.org/releases/2.4/dovecot-2.4.5.tar.gz.sig https://pigeonhole.dovecot.org/releases/2.4/dovecot-pigeonhole-2.4.5.tar.gz https://pigeonhole.dovecot.org/releases/2.4/dovecot-pigeonhole-2.4.5.tar.gz… Binary packages in https://repo.dovecot.org/ Docker images in https://hub.docker.com/r/dovecot/dovecot --- * CVE-2026-27852: Messages with a huge number of From/To/Cc/etc email addresses could result in excessive memory usage. * CVE-2026-33263: Submission: Login service crashes with panic once mail_max_userip_connections limit is reached. * CVE-2026-33604: The SMTP outbound dot-stuffing mechanism does not properly escape dots following a bare \r in message bodies, potentially allowing spoofed emails via malicious end-of-DATA injection. * CVE-2026-33606: Mail content stored by a user can be crafted so that it is interpreted as dsync protocol commands when an administrator later runs dsync with the stream protocol, for example during a migration. * CVE-2026-33607: IMAP LIST command could be used to cause excessive CPU usage. * CVE-2026-40014: IMAP THREAD command could have used excessive amount of CPU processing a single email with a massive number of Message-IDs in References header. * CVE-2026-40015: Invalid IMAP command sent to imap-hibernate process might crash it. * CVE-2026-40017: IMAP THREAD command could have used excessive amount of CPU processing emails with a large number of specially crafted Message-IDs in References header. The fix requires a new dovecot.index.thread file format, which is enabled only after setting dovecot_storage_version or newer. This rebuilds the index, so it will cause some extra CPU usage and extra metacache disk IO usage. It shouldn't cause (much) extra object storage IO, because all the fields should be coming from dovecot.index.cache. * CVE-2026-40203: When IMAP COMPRESS=DEFLATE was enabled, an attacker could send mails into a victim's mailbox and observe network traffic to determine whether a secret message matched a known string by comparing compressed response sizes (a CRIME-style attack). The fix resets the compression dictionary after each IMAP command, preventing information from leaking between commands. * CVE-2026-40205: If multiple OAUTH scopes were required, then this could have been only partially enforced with certain configurations. * CVE-2026-4200: XCLIENT FORWARD allows to forward key only passdb fields without the "forward_" prefix which allows connections from trusted networks to set nopasswd field which allows to skip the authentication. * CVE-2026-42391: Pre-login IMAP ID command could have used excessive amount of memory, causing the process to become killed and disconnecting all the other IMAP connections being proxied by the process. Or alternatively it could have caused excessive CPU usage, slowing down all the other IMAP connections being proxied by the process. * CVE-2026-42392: If URLAUTH is enabled, sending an invalid IMAP URLFETCH can result in an untagged NO response containing uninitialized memory, potentially leaking sensitive data. * CVE-2026-42393: Doveadm password length or API key length could still be determined via timing based attacks. * CVE-2026-42395: XCLIENT FORWARD command from login_trusted_networks could have been used to cause login processes to crash. * CVE-2026-52681: Sieve resource usage (sieve_max_cpu_time) was tracked in the active Sieve binary. Switching to a different active binary could have been used to reset (bypass) the resource usage. * CVE-2026-52687: Using IMAP COMPRESS ZSTD command can cause excessive memory usage in imap-login process, possibly making it reach vsz_limit and kill all the connections being served by the process. Fixed by disabling COMPRESS command with all other compression algorithms than the standard DEFLATE. * CVE-2026-73208: In oauth2, scope/aud checking was done with JWT tokens. Now it requires all scopes. * CVE-2026-73209: Sending IMAP COMPRESS package containing zero-length frames crashes imap or imap-login process. * auth: SIGHUP no longer flushes the passdb cache and SIGUSR2 no longer logs cache statistics. Use "doveadm auth cache flush" and the new "doveadm auth cache status" instead. * auth: The OTP authentication mechanism, the {OTP} password scheme and the passdb set-credentials support have been removed. They were unmaintained and unused. This also drops the passdb_sql_update_query setting. * config: doveconf no longer prints a flat global setting when a top-level named filter overrides the same setting. * doveadm: The doveadm protocol has been bumped to v1.4. The server uses the newer multiplex stream format with clients supporting it. Older clients keep working unchanged. * imap: Change imap_compress_on_proxy default to yes. * lib-dict-extra: Increase dict client request timeout from 30s to 65s, so it stays above the SQL/Cassandra query timeout. * lib-http: HTTP requests are now parsed strictly: obsolete line folding (obs-fold) and a bare LF line terminator are rejected. Both are request desynchronization/smuggling risks. HTTP responses are still parsed leniently. * lib-storage: A '~' in a mailbox name is now escaped only when it is at the beginning of the mailbox name, not at the beginning of every hierarchy part. Directories written by older versions are migrated automatically while listing mailboxes. * lib-var-expand: Add %{time:unix} provider and the epoch, from_epoch, date, iso8601 and escape filters. Deprecates the old time providers. * lib-var-expand: The safe filter must now be the last filter in the chain. * master: Increase the timeout after config reload before killing still running old processes from 6s to 35s, so that lib-master can stop them gracefully first. + config: Support heredoc syntax for multi-line setting values: key = <<EOD ... EOD. doveconf now outputs inline SET_FILE contents (e.g. ssl_ca) using heredoc instead of the "inline:" prefix. The "inline:" form is still accepted. + configure: Build imap-hibernate also when only kqueue notify is available. + doveadm: Add "doveadm auth cache status" command, with --reset for clearing the counters. + doveadm: dump - List all supported dump types, and print the key type also for KEM and unsupported keys. + fts-flatcurve: Add support for phrase searching. This fixes false positives where the searched words existed, but not as a phrase. + fts-flatcurve: Delete the FTS index directory also when a Maildir mailbox is deleted. + imap: Add [THROTTLED] response code to tagged replies when a plugin has throttled the command. + last-login: Add last_login_dict_fields setting for updating multiple dictionary fields at login. + lib-dcrypt: Add ML-KEM-512/768/1024 support with OpenSSL 3. + lib-dcrypt: Support AEAD with Dovecot key encryption. + lib-settings: Expand %{variables} also in strlist and boollist keys. + lib-sql: sqlite - Add sqlite_busy_timeout setting, default 1s. + login-common: Log the destination also when a proxy connection fails. + quota: Update quota-clone also when "doveadm quota recalc" is run. - Fix building on systems with a signed 32-bit time_t. - Fix building with Lua when LUA_LIBS contains linker flags such as -L. - anvil: Fix busy loop eating CPU after an admin socket connection was disconnected. - auth: Fix authentication failing after a password change when the passdb cache entry was verified by an auth worker. - auth: Fix the credentials scheme of one passdb leaking into the next one during a multi-passdb lookup. - auth: oauth2 - Fix losing userdb_* fields during OAUTHBEARER authentication. - auth: passwd-file - Fix %{passdb:...} and %{userdb:...} expansion returning garbage or crashing. - config: Fix crash in "doveconf -f" for a filter that includes a @group. - config: Fix crash when including a default @group into a filter. - config: Fix hiding secrets in doveconf output. - config: Fix startup failures with some settings containing %{variables}. - configure: Fix BUILD_IMAP_HIBERNATE detection. - doc: solr-schema-9.xml - Add the mandatory tokenizer class attribute. - doveadm: compress-connect - Fix writing server input to a non-blocking stdout. - doveadm: fs delete - Fix crash with concurrent async deletes. - doveconf: Fix bogus "Multiple settings matched" error when stdout is redirected to a file that already has content. - dsync: Fix truncating a mailbox attribute value when it is compared to the local one, e.g. truncating a Sieve script. - dsync: backup - Mailbox attributes changed or created only in the destination are now reverted or deleted. - fts-flatcurve: Ignore index directory entries that vanish during iteration. - fts: Don't run FTS optimize on forced resync. - fts: build-mail - Fix accessing Content-Type header buffer out of bounds. - imap-login, pop3-login: Tolerate SASL continuations "+" without a trailing space when proxying authentication. - imap: Don't report FETCH output stream errors as "BUG: Unknown internal error". - imap: Fix hibernation always failing on FreeBSD. - imap: Fix panic on GETMETADATA with an invalid UTF-8 mailbox pattern. - imapc: Don't send SEEEN/UNSEEN to the remote server when private indexes are used. - imapc: Fix SEARCH results pointing at wrong messages after an untagged EXPUNGE. - imapc: Fix SORT returning an empty result when search criteria were used. - imapc: Fix crash when copying a mail that was already expunged in the source mailbox. - imapc: Fix stale SEARCH/SORT results after a STORE in the same session. - imapc: Honor imapc_features=no-search also for SORT. - imapc: Properly handle search criteria that can be sent to remote server. - lib-dcrypt: Don't panic on key algorithms the backend doesn't support. - lib-dcrypt: Fix x9.62 ECDSA signatures randomly failing verification. - lib-dict-backend: cdb - Fix use-after-free of the returned key. - lib-dns-client: Fix handling of a disconnect initiated by the dns-client service. - lib-fs: Fix panic in fs_write_stream_abort(), e.g. when the disk is full during FTS indexing. - lib-index: Fix "File is already open" error when appending to the transaction log while another process is rotating it. This showed up as "NO [SERVERBUG] Internal error occurred." without any logging. - lib-ldap: Fall back to system default CA paths, needed for OpenLDAP built against GnuTLS. - lib-mail: istream-binary-converter - Fix heap use-after-free with a bodyless MIME part. - lib-mail: message-parser - Fix out of bounds read with an empty preamble, fix skipping the epilogue boundary line, and degrade to a re-parse instead of panicking with an inconsistent cached MIME tree. - lib-master: Fix kick reason when the KICK-USER-SIGNAL command arrives late, which logged "Killed with signal 15" instead of "User kicked". - lib-oauth2: jwt - Fix use-after-realloc, guard against an empty body segment and percent-encode bare "." and ".." identifiers. - lib-program-client: Fix panic upon irregular termination. - lib-settings: Fix sorting of the settings history, which caused changed defaults and renames to be ignored once a plugin registered its own history, if dovecot_config_version has been set to greater than 2.4.0. - lib-smtp: Fix assert with an empty broken localpart. - lib-smtp: xclient - Reject an invalid HELO parameter with 501. - lib-sql: pgsql - Fix binary field values for rows after the first. This mainly affected dict-sql maps with hexblob fields. - lib-ssl-iostream: Fix crash at process exit with OpenSSL 4.0. - lib-storage: Don't log an error when the client resets the connection while saving a mail. - lib-storage: Fix crash when reverting a failed mailbox deletion. - lib-storage: Fix decoded size calculation for base64 attachments, which could delete the cache record of a mail with a detached attachment. - lib-storage: Fix handling escaped mailbox names in the mailbox list index. - lib-storage: Fix rewriting non-NFC subscriptions with mUTF-7 storage names, which caused repeated rename errors. - lib-storage: Fix searching flags when the view is not up to date. This broke e.g. a pipelined UID STORE +FLAGS \Deleted followed by UID EXPUNGE. - lib-storage: Fix the mailbox vsize header not being repaired when it is corrupted, causing wrong mailbox sizes to be reported. - lib-storage: thread - Fix panic when running IMAP THREAD in multiple connections in parallel. - lib-var-expand: Reject an empty separator in the index filter, which caused an infinite loop. - lib: Fix crash and out of bounds reads when decoding IDN addresses. Reachable only with the experimental mail UTF-8 support enabled. - lib: ioloop - Fix panic and delayed timeouts when time moves forwards. - lib: ostream-multiplex - Fix stalls, busy loops and a panic when streaming data through a multiplexed connection, e.g. IMAP FETCH through a login proxy or TLS connections. - login-common: Fix connection hanging if an ostream write failed. This happened at least with HAProxy health check connections. - login-common: Fix real_remote_ip being looked up incorrectly. - login-common: Reject proxy credentials with ASCII control characters. - login-proxy: Fix "doveadm kick" for proxied connections in high-security mode, and log "Kicked by admin" as the reason. - maildir: Fix random SEARCH failures when another session concurrently expunges mails. - quota: Fix maildir quota dropping to zero after IMAP MOVE or REPLACE. - submission-login: proxy - Fix crash and unbounded memory usage with a multi-line or malformed AUTH reply from the backend. --- * CVE-2026-33605: managesieve-login: Pre-auth crash. An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating. * CVE-2026-40019: v2.4.3 regression: managesieve-login pre-auth infinite loop. An unauthenticated attacker can send a truncated quoted argument to the ManageSieve login process, which makes it spin in an infinite loop consuming CPU. * CVE-2026-42007: sieve-editheader: An attacker that has valid credentials can use a Sieve script with the editheader extension to trigger a use-after-free in the mail editing code, and to write memory contents beyond the intended buffer in the delivered mail. * lib-sieve: sieve_max_cpu_time now defaults to 30s globally, so the limit also applies to MDA delivery. Previously the global default was unlimited and only imap_sieve used 30s. The old defaults are kept for older dovecot_config_version values. * lib-sieve: enotify - The number of notify actions performed during a single script execution is now limited to 10 by default. See the new sieve_notify_max_notifications setting. * lib-sieve: enotify - A single "mailto:" notify action is now limited to 8 recipients and 16 additional headers by default. See the new sieve_notify_mailto_max_recipients and sieve_notify_mailto_max_headers settings. * imap-filter-sieve: FILTER SIEVE SCRIPT literals larger than sieve_max_script_size are now rejected before the script is read. - lib-sieve: Fix stack overflow occurring when a script requires the same extension repeatedly. - lib-sieve: encoded-character - Fix integer overflow parsing ${unicode:...} values with 9 or more hex digits. - lib-sieve: variables - Fix integer overflow parsing numeric variable index. - lib-sieve: regex - Fix panic occurring when more than 8 group values are matched. - lib-sieve: ldap - Fix LDAP settings missing from the LDAP storage plugin. - managesieve-login: Fix capability reporting when Sieve settings use %variables.

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Dovecot Security Advisory OXDC-2026-0002
by Aki Tuomi 12 May '26

12 May '26

Hi! We're sharing our latest advisory with you and like to thank everyone who contributed in finding and solving those vulnerabilities. This advisory is also published at https://documentation.open-xchange.com/dovecot/security/advisories/html/202… --- Classification: TLP:GREEN Internal reference: DOV-8967 Type: CWE-235 (Improper Handling of Extra Parameters) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 3.1.4, OX Dovecot CE core 2.4.3 First fixed revision: OX Dovecot Pro core 3.1.5, OX Dovecot CE core 2.4.4 Discovery date: 2026-03-29 Solution date: 2026-05-05 Disclosure date: 2026-05-05 Researcher credits: caprinuxx@yeswehack CVE: CVE-2026-27851 CVSS: 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N) Details: lib-var-expand: Safe filter leaks to all following pipelines. When safe filter is used with variable expansion, all following pipelines on the same string are incorrectly interpreted as safe too, enabling unsafe data to be unescaped. Risk: This can enable SQL / LDAP injection attacks when used in authentication. No publicly available exploits are known. Solution: Avoid using safe filter until on fixed version. --- Internal reference: DOV-8948 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 2.3.0 First fixed revision: OX Dovecot Pro core 3.1.5, OX Dovecot CE core 2.4.4 Discovery date: 2026-03-24 Solution date: 2026-05-05 Disclosure date: 2026-05-05 Researcher credits: djvirus@yeswehack CVE: CVE-2026-40016 CVSS: 5.3 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H) Details: Sieve :contains/:matches O(N×M) Substring Match Bypasses sieve_max_cpu_time Limit (130× Overrun). Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU time limits for Sieve up to 130 times of the configured limit. Risk: Attacker can use this to degrade server performance and bypass configured CPU time limits for Sieve scripts. No publicly available exploits are known. Solution: Install fixed version, or alternatively prevent direct access to Sieve scripts via ManageSieve or local access. --- Internal reference: DOV-9030 Type: CWE-99 (Improper Control of Resource Identifiers ('Resource Injection')) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 3.1.0, OX Dovecot CE core 2.4.0 First fixed revision: OX Dovecot Pro core 3.1.5, OX Dovecot CE core 2.4.4 Discovery date: 2026-04-08 Solution date: 2026-05-05 Disclosure date: 2026-05-05 Researcher credits: ylwango613@yeswehack CVE: CVE-2026-33603 CVSS: 6.8 (CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N) Details: login: Base64 input can contain tabs that bypass IPC protection. Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel binding. This requires that the attacker is able to position itself between Dovecot and the client connection. Risk: If successful, the attacker can eavesdrop communications between Dovecot and client as MITM proxy. No publicly available exploits are known. Solution: Install fixed version. --- Internal reference: DOV-9040 Type: CWE-284 (Improper Access Control) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 2.3.0 First fixed revision: OX Dovecot Pro core 3.1.5, OX Dovecot CE core 2.4.4 Discovery date: 2026-04-08 Solution date: 2026-05-05 Disclosure date: 2026-05-05 Researcher credits: ilhamaf@yeswehack CVE: CVE-2026-40020 CVSS: 3.1 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L) Details: IMAP folders can be shared-spammed to everyone. Attacker can use the IMAP SETACL command to inject the anyone permission to user's dovecot-acl file even if imap_acl_allow_anyone=no. This causes folders to be spammed to all users. Risk: The impact is limited to being able to spam folders to other users, no unexpected access is gained. No publicly available exploits are known. Solution: Install to fixed version. --- Internal reference: DOV-9138 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 3.0.5, OX Dovecot Pro core 3.1.4, OX Dovecot CE core 2.4.3 First fixed revision: OX Dovecot Pro core 3.1.5, OX Dovecot CE core 2.4.4 Discovery date: 2026-04-27 Solution date: 2026-05-05 Disclosure date: 2026-05-05 Researcher credits: D4RKCYPH3R@yeswehack CVE: CVE-2026-42006 CVSS: 4.3 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L) Details: imap-login: Excessive memory usage DoS - Try 2. An attacker can cause uncontrolled memory usage with excessive bracing over IMAP. The fix in CVE-2026-27857 was incomplete, only blocking one way of doing this, so there was still another way left open. In particular, the fix was for closing braces, but you could still use open braces to bypass the limit. Risk: Using excessive bracing, attacker can cause memory usage up to configured memory limit. No publicly available exploits are known. Solution: Install fixed version, or configure vsz_limit for imap process to low value.

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Dovecot and Pigeonhole v2.4.4 Released
by Aki Tuomi 12 May '26

12 May '26

Hi! We are happy to publish version 2.4.4 of Dovecot and Pigeonhole. These contain CVEs, discovered by external researches. The majority of these have been discovered with help of automated code analysis tools like claude code security, which is why some of these are rather old, missed bugs. No new supported distros have been added or old removed, no new dependencies have been added. Note that there are experimental features in 2.4, one is enabled with `--enable-experimental-mail-utf8`, and another with `--enable-experimental-imap4rev2`, and you also need to set mail_utf8_extensions=yes and imap4rev2_enabled=yes to enable them in config. https://dovecot.org/releases/2.4/dovecot-2.4.4.tar.gz https://dovecot.org/releases/2.4/dovecot-2.4.4.tar.gz.sig https://pigeonhole.dovecot.org/releases/2.4/dovecot-pigeonhole-2.4.4.tar.gz https://pigeonhole.dovecot.org/releases/2.4/dovecot-pigeonhole-2.4.4.tar.gz… Binary packages in https://repo.dovecot.org/ Docker images in https://hub.docker.com/r/dovecot/dovecot --- * CVE-2026-27851: lib-var-expand: Safe filter marks all following pipelines safe. * CVE-2026-33603: auth: CRAM-SHA-*-PLUS channel binding could be faked. MITM attacker with a certificate trusted by the client could have bypassed the requirement for channel binding. * CVE-2026-40020: IMAP folders can be shared-spammed to everyone. * CVE-2026-42006: An attacker can cause uncontrolled memory usage with excessive bracing over IMAP. The fix in CVE-2026-27857 was incomplete. * indexer-worker, quota-status, script-login, program-client-local: Root privileges are now dropped permanently before serving requests. * indexer-worker: Default restart_request_count changed to 1 to work correctly after permanent root privilege drop. * lmtp: Add back service_extra_groups=$SET:default_internal_group that was incorrectly removed in v2.4.3. * master: inet_listener_reuse_port has been replaced by service_reuse_port. The new setting properly pre-creates all listener sockets at startup and assigns one unique socket per process. Using this allows evenly distributing incoming connections to login processes. See https://doc.dovecot.org/latest/core/config/service.html#service_reuse_port for details. - auth: Fix LDAP escaping of 0x13 control character. - auth: Use timing-safe comparison for certificate and public key fingerprints. - fts: Correctly handle internal http-client response errors. - fts: Don't send request to Tika if there is no body text. - fts: Fix address header indexing for RFC 2047 encoded-words. - fts: tika, fts-solr: Fix use-after-free crash during DNS lookup. - imap: Fix assertion panic on invalid REPLACE 0 command. - lib-auth-client: Avoid "unknown id" errors for aborted auth requests. - lib-dcrypt: Fix potential crash if trying to access untrusted/corrupted keys. - lib-dcrypt: Improve error message if keys aren't in hex format as expected. - lib-index: Fix potential crash if fsck fails. - lib-ldap: Fix using OpenLDAP default CA when ssl_client_ca_dir/file is unset. v2.4.3 regression. - lib-master, master: Fix behavior for services with client_limit>1 and restart_request_count so that processes reaching restart_request_count are no longer counted towards process_limit. - lib-master: Fix crash when reaching client_limit with restart_request_count>1. - lib-master: haproxy - Don't trust client certificate common name when HAProxy reports verification failure. - lib-sasl: cram-md5 - Fix out of bounds memory read. - lib-sasl: oauth2 - Fix one byte out of bounds read. - lib-sql: cassandra - Fix reusing Cassandra SSL connections. - lib-sql: sqlite - Fix sqlite_journal_mode=wal to actually work. - lib-storage: Auto-rename non-NFC subscription file entries to NFC on read. - lib-storage: Prevent non-atom SEARCH keywords from causing IMAP command injection. - lib-var-expand-crypt: Return error if hex decoding fails. - lib-var-expand: Fix crash (SIGFPE) with non-positive divisor for / and %. - log: Fix memory leak at deinit. - login-common: When process is full, don't destroy clients waiting on master auth. - login-proxy: Fix crash with rawlog and multiplexing during reconnection. - mail-compress: Fix panic when save method unavailable. - mail-crypt: Fix crash when HMAC-based algorithm is used. - mail-crypt: Use AEAD instead of HMAC with ChaCha20-Poly1305. - mdbox: Create files with O_NOFOLLOW. - push-notification: ox - Fix use-after-free crash during DNS lookup. - quota: quota-status - Limit input buffer size to 1 kB. ––- * CVE-2026-40016: sieve :contains and :matches operators could have been using excessive amount of CPU. Limit the CPU to sieve_max_cpu_time. - Fix potential crashes parsing corrupted Sieve binaries. - lib-sieve: matches - Fix trailing literal match when it fills value exactly. v2.4.3 regression.

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Source tarballs for dovecot 2.4.3 republished
by Aki Tuomi 10 Apr '26

10 Apr '26

Hi! We have republished the source tarballs for 2.4.3 due to missing man pages in the tarball. Regards, AKi

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Dovecot Security Advisory OXDC-2026-0001
by Aki Tuomi 27 Mar '26

27 Mar '26

Hi! We're sharing our latest advisory with you and like to thank everyone who contributed in finding and solving those vulnerabilities. This advisory is also published at https://documentation.open-xchange.com/dovecot/security/advisories/html/202… --- Internal reference: DOV-7830 Type: CWE-1250 (Improper Preservation of Consistency Between Independent Representations of Shared State) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot CE core 2.4.0 First fixed revision: OX Dovecot CE core 2.4.1 Discovery date: 2025-07-24 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: Erik <erik(a)broadlux.com> CVE: CVE-2025-30189 CVSS: 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N) Details: v2.4 regression: auth cache broken with several passdb / userdb. When cache is enabled, some passdb/userdb drivers incorrectly cache all users with same cache key, causing wrong cached information to be used for these users. Risk: After cached login, all subsequent logins are for same user. No publicly available exploits are known. Solution: Install fixed version or disable caching either globally or for the impacted passdb/userdb drivers. --- Internal reference: DOV-8349 Type: CWE-20 (Improper Input Validation) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot CE core 2.4.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2025-11-04 Solution date: 2026-03-27 Disclosure date: 2026-03-27 CVE: CVE-2025-59028 CVSS: 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L) Details: Invalid base64 authentication can cause DoS for other logins. When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all active authentication sessions to fail. Risk: Invalid BASE64 data can be used to DoS a vulnerable server to break concurrent logins. No publicly available exploits are known. Solution: Install fixed version or disable concurrency in login processes (heavy perfomance penalty on large deployments). --- Internal reference: DOV-8508 Type: CWE-20 (Improper Input Validation) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot CE core 2.4.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2025-11-29 Solution date: 2026-03-27 Disclosure date: 2026-03-27 CVE: CVE-2025-59032 CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) Details: v2.4/v3.1 regression: Pigeonhole: ManageSieve panic occurs with sieve-connect as a client. ManageSieve AUTHENTICATE command crashes when using literal as SASL initial response. Risk: This can be used to crash ManageSieve service repeatedly, making it unavailable for other users. No publicly available exploits are known. Solution: Control access to ManageSieve port, or disable the service if it's not needed. Alternatively upgrade to a fixed version. --- Internal reference: DOV-8584 Type: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 2.3.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2025-12-29 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: cavid@yeswehack CVE: CVE-2025-59031 CVSS: 4.3 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N) Details: decode2text.sh OOXML extraction may follow symlinks and read unintended files during indexing. Dovecot has provided a script to use for attachment to text conversion. This script unsafely handles zip-style attachments. Risk: Attacker can use specially crafted OOXML documents to cause unintended files on the system to be indexed and subsequently ending up in FTS indexes. No publicly available exploits are known. Solution: Do not use the provided script, instead, use something else like FTS tika. --- Internal reference: DOV-8591 Type: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 2.3.0 First fixed revision: OX Dovecot CE core 2.4.0 Discovery date: 2026-01-07 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: strokep@yeswehack CVE: CVE-2026-0394 CVSS: 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N) Details: auth: Path traversal in passwd-file passdb using `%d` (domain) escapes base directory and opens `/etc/passwd`Pre-auth path traversal in passwd-file passdb using `%d` (domain) escapes base directory and opens `/etc/passwd`. When dovecot has been configured to use per-domain passwd files, and they are placed one path component above /etc, or slash has been added to allowed characters, path traversal can happen if the domain component is directory partial. Risk: This allows inadvertently reading /etc/passwd (or some other path which ends with passwd). If this file contains passwords, it can be used to authenticate wrongly, or if this is userdb, it can unexpectly make system users appear valid users. No publicly available exploits are known. Solution: Upgrade to fixed version, or use different authentication scheme that does not rely on paths. Alternatively you can also ensure that the per-domain passwd files are in some other location, such as /etc/dovecot/auth/%d. --- Internal reference: DOV-8775 Type: CWE-90 (Improper Neutralization of Special Elements used in an LDAP Query ('LDAP Injection')) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot CE core 2.4.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2026-02-20 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: cookiejack15@yeswehack CVE: CVE-2026-27860 CVSS: 3.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N) Details: v2.4/v3.1 regression: auth-ldap is not escaping usernames. If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authentication. Risk: This leads to potentially bypassing restrictions and allows probing of LDAP structure. No publicly available exploits are known. Solution: Do not clear out auth_username_chars, or install fixed version. --- Internal reference: DOV-8781 Type: CWE-89 (Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot CE core 2.4.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2026-02-23 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: whisperer@yeswehack CVE: CVE-2026-24031 CVSS: 7.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L) Details: v2.4/v3.1 regression: SQL injection allows bypassing authentication. Dovecot SQL based authentication can be bypassed when auth_username_chars is cleared by admin. Risk: This vulnerability allows bypassing authentication for any user and user enumeration. No publicly available exploits are known. Solution: Do not clear auth_username_chars. If this is not possible, install latest fixed version. --- Internal reference: DOV-8787 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot CE core 2.4.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2026-02-24 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: djvirus@yeswehack CVE: CVE-2026-27859 CVSS: 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L) Details: v3.0.2+ regression: Message headers MIME parameter parsing can cause excessive CPU usage. A mail message containing excessive amount of RFC 2231 MIME parameters causes LMTP to use too much CPU. Risk: A suitably formatted mail message causes mail delivery process to consume large amounts of CPU time. No publicly available exploits are known. Solution: Use MTA capabilities to limit RFC 2231 MIME parameters in mail messages, or upgrade to fixed version where the processing is limited. --- Internal reference: DOV-8816 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 2.3.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2026-02-27 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: whisperer@yeswehack CVE: CVE-2026-27857 CVSS: 4.3 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L) Details: imap-login: Excessive memory usage DoS. Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Risk: Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. No publicly available exploits are known. Solution: Install fixed version, there is no other remediation. --- Internal reference: DOV-8818 Type: CWE-400 (Uncontrolled Resource Consumption) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 2.3.0, OX Dovecot CE core 2.4.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2026-02-28 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: ilyar@yeswehack CVE: CVE-2026-27858 CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) Details: managesieve-login out-of-memory DoS. Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory. Risk: Attacker can force managesieve-login to be unavailable by repeatedly crashing the process. No publicly available exploits are known. Solution: Protect access to managesieve protocol, or install fixed version. --- Internal reference: DOV-8830 Type: CWE-287 (Improper Authentication) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 2.3.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2026-03-04 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: bksparajuli@yeswehack CVE: CVE-2026-27856 CVSS: 7.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N) Details: doveadm: Credentials verified without timing safety. Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An attacker can use this to determine the configured credentials. Risk: Figuring out the credential will lead into full access to the affected component. No publicly available exploits are known. Solution: Limit access to the doveadm http service port, install fixed version. --- Internal reference: DOV-8859 Type: CWE-294 (Authentication Bypass by Capture-replay) Component: core Report confidence: Confirmed Solution status: Fixed by vendor Last affected revision: OX Dovecot Pro core 2.3.0 First fixed revision: OX Dovecot CE core 2.4.3 Discovery date: 2026-03-09 Solution date: 2026-03-27 Disclosure date: 2026-03-27 Researcher credits: hamizanazman@yeswehack CVE: CVE-2026-27855 CVSS: 6.8 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N) Details: auth: OTP driver vulnerable to replay attack. Dovecot OTP authentication is vulnerable to replay attack under specific conditions. If auth cache is enabled, and username is altered in passdb, then OTP credentials can be cached so that same OTP reply is valid. Risk: An attacker able to observe an OTP exchange is able to log in as the user. No publicly available exploits are known. Solution: If authentication happens over unsecure connection, switch to SCRAM protocol. Alternatively ensure the communcations are secured, and if possible switch to OAUTH2 or SCRAM.

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Dovecot and Pigeonhole v2.4.3 released
by Aki Tuomi 27 Mar '26

27 Mar '26

Hi! We are happy to publish version 2.4.3 of Dovecot and Pigeonhole. These contain several CVEs, discovered by external researches. The majority of these have been discovered with help of automated code analysis tools like claude code security, which is why some of these are rather old, missed bugs. No new supported distros have been added or old removed, no new dependencies have been added. Note that there are experimental features in 2.4, one is enabled with `--enable-experimental-mail-utf8`, and another with `--enable-experimental-imap4rev2`, and you also need to set mail_utf8_extensions=yes and imap4rev2_enabled=yes to enable them in config. https://dovecot.org/releases/2.4/dovecot-2.4.3.tar.gz https://dovecot.org/releases/2.4/dovecot-2.4.3.tar.gz.sig https://pigeonhole.dovecot.org/releases/2.4/dovecot-pigeonhole-2.4.3.tar.gz https://pigeonhole.dovecot.org/releases/2.4/dovecot-pigeonhole-2.4.3.tar.gz… Binary packages in https://repo.dovecot.org/ Docker images in https://hub.docker.com/r/dovecot/dovecot --- * CVE-2025-59028: Invalid base64 authentication can cause DoS for other logins. * CVE-2025-59031: decode2text.sh OOXML extraction may follow symlinks and read unintended files during indexing. Fixed by dropping the script. * CVE-2026-24031: SQL injection possible if auth_username_chars is configured empty. Fixed escaping to always happen. v2.4 regression. * CVE-2026-27859: Excessive RFC 2231 MIME parameters in email would cause excessive CPU usage. Fixed by limiting number of parameters to process. * CVE-2026-27860: LDAP query injection possible if auth_username_chars is configured empty. Fixed escaping to always happen. v2.4 regression. * CVE-2026-27857: Sending excessive parenthesis causes imap-login to use excessive memory. * CVE-2026-27856: Doveadm credentials were not checked using timing-safe checking function. * CVE-2026-27855: OTP driver vulnerable to replay attack. * Remove default service/*/service_extra_groups=$SET:default_internal_group. They are now replaced by default mail_access_groups=$SET:default_internal_group. * The version file has been renamed as version.txt to avoid clash with C++ headers. * auth: oauth2 - Do not export token automatically, must be exported using fields. * config: Don't accept 0 as meaning unlimited anymore for last_valid_uid, last_valid_gid, mail_cache_max_headers_count, mail_cache_max_header_name_length, mail_vsize_bg_after_count, mail_sort_max_read_count, message_max_size, submission_max_recipients and quota_mail_size. * imap, pop3: Don't autoexpunge if Dovecot is shutting down or process is killed. * imap: LIST - Handle invalid mUTF-7 mailbox names as never matching anything * lazy-expunge: Change lazy_expunge_only_last_instance default to yes. * lda: Use EX_TEMPFAIL (75) if configuration is invalid instead of 89. v2.4 regression. * lib-master: Increase ANVIL_DEFAULT_LOOKUP_TIMEOUT_MSECS from 5s to 30s * lib: crc32 - Use zlib's built-in CRC32 function + Improve UTF-8 support for mail storage. + auth: Add default auth-token UNIX socket for token-based authentication. + doc: solr-config-9.xml - Make it compatible with Solr 9.8.0 + doveadm: dsync - Search mails when exporting to reduce number of mails exported by dsync-server. + dovecot-sysreport: Add -D|--destdir support. + imap, imap-hibernate: Use DOVECOT-TOKEN authentication for unhibernation. Default imap-master socket permissioms have been changed due to this. + imap: Add APPENDLIMIT capability when configured with quota_mail_size. + imap: Support STATUS (DELETED) for IMAP4rev2. + imapc: Add support for SEARCH MIMEPART + imapc: Improve error forwarding. + imapc: Support SORT and ESORT extensions. + imapc: Support STATUS (DELETED) for IMAP4rev2. + lib-sql: Support parameterized queries. + lib-test: Add new test-dir API for better temporary test directory handling. + lmtp: Advertize SIZE capability when configured with quota_mail_size. + lmtp: Support XCLIENT DESTADDR and DESTPORT + pop3-login: proxy - Add support for XCLIENT DESTIP and DESTPORT + submission-login: proxy - Add support for XCLIENT DESTIP and DESTPORT + Various optimizations have been made to the code. - Fix building dovecot with BSD, Solaris and macOS. - auth: Crash would occur if users were iterated but userdb_ldap_iterate_fields was not set. - auth: Fix request leak when client authenticates with unsupported mechanism. - auth: Some passdbs would default to PLAIN instead of CRYPT scheme. - config: Section and setting names could have been intermixed, resulting in the setting being silently ignored. - configure: Fix checking if BUILD_IMAP_HIBERNATE is set - doveadm: dsync - -e parameter was handled wrong with dsync-server. - fts-flatcurve: Mailbox leak would occur if mailbox failed to open. - imap: Fix potential issues with unhibernation and process state handling. - imapc: SEARCH failure handling was done wrong. - imapc: UID STORE commands included extra comma in uidset. - lib-auth-client: auth-master - Fix panic when reconnecting after handshake timeout. - lib-compression: Lz4 algorithm would assert-crash with malicious data. - lib-dcrypt: Fix digest algorithm handling. - lib-dict: Escape username paths to prevent traversal issues with dict-fs. - lib-http: Fix HTTP parsing edge cases and state handling. - lib-iostream: Disallow empty ssl_min_protocol. - lib-json: Fix incorrect character handling logic. - lib-ldap: Fix various TLS related bugs. - lib-mail: Fix charset translation and MIME parsing edge cases. - lib-mail: Fix multiple bounds checks and parsing issues in message handling. - lib-var-expand: Multiple fixes and improvements for expansion handling. - lib: Fix punycode decoding out-of-bounds reads. - lib: Fix unicode normalization edge cases causing crashes. - lib-http: Chunked transfer trailer size was not limited. - login-common: Improve logging and internal error handling. - login-common: login_log_format_elements was split by spaces naively, which could break variable expansion. Use template aware splitting now. - master: Dovecot would fail to start if listen directive was used and dovenull or dovecot user was missing. - pop3c: Connection might've hung with SSL. - util: Fix handling of environment variables containing control characters. - Many other bugs have been fixed. --- * CVE-2026-27858: managesieve-login can allocate large amount of memory during authentication. * CVE-2025-59032: ManageSieve panic occurs with sieve-connect as a client. * lib-sieve: Don't accept 0 as meaning unlimited anymore for sieve_quota_script_count and sieve_quota_storage_size. * managesieve-login: If mail_max_userip_connections is reached, return LIMIT/CONNECTIONS resp-code. * managesieve-login: proxy - Return unexpected backend failures as TRYLATER/NORETRY resp-code. * managesieve: Remove default service_extra_groups=$SET:default_internal_group. + managesieve-login: proxy - Add support for XCLIENT DESTIP and DESTPORT. - imapsieve: Fix panic occurring upon implicit flag changes. - lib-sieve: include-extension - Fix crash occurring when previous global command has no arguments. - lib-sieve: Fix erroneous attempt to read active script for non-personal storage. - lib-sieve: ldap: Fix linking non-shared LIBDOVECOT.

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Republish of 2.4.2
by Aki Tuomi 10 Mar '26

10 Mar '26

Hi all! We have republished 2.4.2 packages to fix some packaging issues with Pigeonhole. Please note that for now dovecot-sieve and dovecot-managesieved will get installed together due to dependency issues. Kind regards, Aki Tuomi

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Republish of dovecot 2.4.2 packages
by Aki Tuomi 08 Jan '26

08 Jan '26

Hi! Due to mistake in RHEL 10 packaging, we have republished packages for 2.4.2. Content is still the same, build number has increased by one. The important change is that there is now pigeonhole package for RHEL 10. You can find the packages at https://repo.dovecot.org/ as usual. Kind regards, Aki Tuomi

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