May 2026 - dovecot - dovecot.org

Sync'ing two dovecot servers
by Marc Singer 12 May '26

12 May '26

Greetings, I was pleased to see that dovecot has a sync function in doveadm. So far, other tools for moving mailbox contents from one server to another has not been successful. However. Perhaps I don't understand how this should work. I have a new containerized dovecot v2.4.2 # 2.4.2 (0962ed2104): /etc/dovecot/dovecot.conf # OS: Linux 6.12.63+deb13-amd64 x86_64 and I have an existing dovecot running in a VPS: # 2.3.19.1 (9b53102964): /etc/dovecot/dovecot.conf # Pigeonhole version 0.5.19 (4eae2f79) # OS: Linux 6.1.0-35-amd64 x86_64 Debian 12.11 I want to move one user, as a test. I execute this in the container. # doveadm sync -R1 -u USER tcps:OLD_SERVER:993 doveadm(USER): Error: conn OLD_SERVER:993 (IP:993): doveadm server sent invalid handshake: * OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE LITERAL+ AUTH=PLAIN AUTH=LOGIN] Dovecot (Debian) ready. doveadm(USER): Error: cmd sync: Disconnected from remote: Connection closed I'm pretty sure that doveadm sync was able to negotiate the TLS connection. I don't see what it could object to in the sign-on. What am I missing? Cheers -- /Marc Oscar Singer/ *Woollysoft* Dial 817.1823.602.1+ from right to left. Greetings, I was pleased to see that dovecot has a sync function in doveadm. So far, other tools for moving mailbox contents from one server to another has not been successful. However. Perhaps I don't understand how this should work. I have a new containerized dovecot v2.4.2 # 2.4.2 (0962ed2104): /etc/dovecot/dovecot.conf # OS: Linux 6.12.63+deb13-amd64 x86_64 and I have an existing dovecot running in a VPS: # 2.3.19.1 (9b53102964): /etc/dovecot/dovecot.conf # Pigeonhole version 0.5.19 (4eae2f79) # OS: Linux 6.1.0-35-amd64 x86_64 Debian 12.11 I want to move one user, as a test. I execute this in the container. # doveadm sync -R1 -u USER tcps:OLD_SERVER:993 doveadm(USER): Error: conn OLD_SERVER:993 (IP:993): doveadm server sent invalid handshake: * OK [CAPABILITY IMAP4rev1 SASL-IR LOGIN-REFERRALS ID ENABLE IDLE LITERAL+ AUTH=PLAIN AUTH=LOGIN] Dovecot (Debian) ready. doveadm(USER): Error: cmd sync: Disconnected from remote: Connection closed I'm pretty sure that doveadm sync was able to negotiate the TLS connection. I don't see what it could object to in the sign-on. What am I missing? Cheers -- Marc Oscar Singer Woollysoft Dial 817.1823.602.1+ from right to left.

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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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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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Changed location of index files
by Lafiel Elentari 11 May '26

11 May '26

Hello. After upgrading to version 2.4, index files were moved to the user's home directory, and the `mail_path = ~/mail` parameter was no longer taken into account when processing index files. In addition, indexes for the `INBOX` folder no longer respect the `mail_index_path=` parameter and are stored in the `./INBOX/dovecot.index.*` folder, although they should be stored in the same folder where the messages are stored, given the current configuration. My configuration: ``` mail_home = mail_inbox_path = mail_index_path = mail_path = ~/mail userdb declarative { passwd_file_path = /var/data/mail/dovecot/passdb driver = passwd-file fields { home = /var/data/mail/vmail/%{user | domain}/%{user | username} mail_index_path = /var/data/mail/vmail/%{user | domain }/%{user | username} } } ``` Current location of index files: ``` /var/data/mail/vmail/example.com/user ├── INBOX │ ├── dovecot.index.cache │ └── dovecot.index.log ├── Sent │ ├── dovecot.index.cache │ └── dovecot.index.log ├── Drafts │ └── dovecot.index.log ├── Junk │ └── dovecot.index.log ├── Trash │ ├── dovecot.index.cache │ └── dovecot.index.log ├── dovecot.list.index ├── dovecot.list.index.log └─── mail ├── cur ├── new ├── tmp ├── Sent │ ├── cur │ ├── new │ ├── tmp │ └── dovecot-uidlist ├── Drafts │ ├── cur │ ├── new │ ├── tmp │ └── dovecot-uidlist ├── Junk │ ├── cur │ ├── new │ ├── tmp │ └── dovecot-uidlist ├── Trash │ ├── cur │ ├── new │ ├── tmp │ └── dovecot-uidlist ├── subscriptions ├── dovecot.mailbox.log ├── dovecot-uidlist ├── dovecot-uidvalidity └── dovecot-uidvalidity.69d94118 ``` Expected location of index files according to configuration: ``` /var/data/mail/vmail/example.com/user └─── mail ├── cur ├── new ├── tmp ├── Sent │ ├── cur │ ├── new │ ├── tmp │ ├── dovecot.index │ ├── dovecot.index.cache │ ├── dovecot.index.log │ └── dovecot-uidlist ├── Drafts │ ├── new │ ├── tmp │ ├── cur │ ├── dovecot.index │ ├── dovecot.index.cache │ ├── dovecot.index.log │ └── dovecot-uidlist ├── Junk │ ├── new │ ├── tmp │ ├── cur │ ├── dovecot.index │ ├── dovecot.index.cache │ ├── dovecot.index.log │ └── dovecot-uidlist ├── Trash │ ├── cur │ ├── new │ ├── tmp │ ├── dovecot.index │ ├── dovecot.index.cache │ ├── dovecot.index.log │ └── dovecot-uidlist ├── dovecot.index ├── dovecot.index.cache ├── dovecot.index.log ├── dovecot.list.index ├── dovecot.list.index.log ├── dovecot.mailbox.log ├── dovecot-uidlist ├── dovecot-uidvalidity ├── dovecot-uidvalidity.69d94118 └── subscriptions ``` -- Best regards, Lafiel Elentari mailto:lafiel@elven.pw

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Dovecot 2.3.21.1 missing dbox-Mails folder causes IMAP folder which can not be deleted? Possible known bug?
by Benoit Panizzon 11 May '26

11 May '26

Hi Team Running Dovecot 2.3.21.1 in an ISP environment using dbox format as storage and built in dovecot replication to a secondary storage. => I know, it's not new - migration to 2.4 with completely replacing replication is pending. For quite some time we are fighting issues with customers which are unable to delete IMAP folder. Those folder end up in status \NoSelect When you issue a 'delete' for the folder, it is successful, but either the folder is back after logout/login or back right away when you list the folders. Usual remedy: completely delete mail index of affected mailbox on both, primary and secondary storage, delete complete mail storage on secondary, resync with doveadm force-resync, cross filters. Now I had a mailbox where even this did not solve the issue - but I noticed something weird. . delete "mailbox" => OK . delete "mailbox" => OK . create "mailbox" => OK . create "mailbox" => Mailbox does already exist . delete "mailbox" => OK . delete "mailbox" => Mailbox does not exist Now the Mailbox is gone from the file system and is not shown with list anymore. Now I had a closer look at the next affected mailbox on the filesystem. IMAP Foldername: LIST (\Noselect \HasNoChildren) "." INBOX.brokenmbox Filesystem, directories: INBOX/brokenmbox/ => There is no content, no hidden files inside the folder 'broeknmbox' . delete "INBOX.brokenmbox" => OK Checking Filesystem. Nothing changed, still the same. . create "INBOX.brokenmbox" => OK Checking Filesystem: Now we have: INBOX/broeknmbox/dbox-Mails/ all empty. . delete "INBOX.brokenmbox" => OK Checking Filesystem: broeknmbox/dbox-Mails/ are both gone within INBOX! Conclusion: Dovecot seems to get confused, when a directory without dbox-Mails subdirectory exists, fails to delete such directories but still lists them as IMAP folders. Is this a known bug? Is there anything which is know to cause this issue which we could tweak at our configuration? Mit freundlichen Grüssen -Benoît Panizzon- -- I m p r o W a r e A G - Leiter Commerce Kunden ______________________________________________________ Zurlindenstrasse 29 Tel +41 61 826 93 00 CH-4133 Pratteln Fax +41 61 826 93 01 Schweiz Web http://www.imp.ch ______________________________________________________

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Migration Planning for Dovecot 2.3 to 2.4
by Gregory Carter 05 May '26

05 May '26

Hello so I have started planning my 2.3 to 2.4 migration and finished the lab work today for that process. Does anyone know of any tools to migrate the configs from 2.3 to 2.4? Also if you are running 2.4 I would like to hear from you as to how well it is working out. Thanks. Hello so I have started planning my 2.3 to 2.4 migration and finished the lab work today for that process. Does anyone know of any tools to migrate the configs from 2.3 to 2.4? Also if you are running 2.4 I would like to hear from you as to how well it is working out. Thanks.

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Dovecot sieve, help !
by Tommy Berglund 03 May '26

03 May '26

Hi! I need help and advice on how to get sieve working. Postfix dovecot works to receive and send mail but I can't get sieve to work. Domain and user are virtual in mariadb. Tips are welcome. Doveconf -n attached.

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mail_inbox_path in manual
by Daniel Convissor (business) 01 May '26

01 May '26

Hi: Recently upgraded Debian to version 13/Trixie, which brings Dovecot up to 2.4 (with its significant configuration file changes). As mentioned on this list, Debian decided to manually put mail_inbox_path in their distribution's config files (and set it to /var/mail/%{user}).[1] This resulted in mayhem for me because that's not where our mail is. I assume this has happened to others as well. I figured out the problem by looking at mail.log after adding mail_debug=yes to my local Dovecot config file. Perhaps Dovecot's manual can be updated to clarify the situation, please? The Mail Location page[2] warns admins to not touch this setting. The upgrade page[3] does not mention needing to look out for Debian's choice. (Granted, this is a Debian problem, but the Dovecot manual is where people turn to figure out what is happening.) Thank you, --Dan [1] https://dovecot.org/mailman3/archives/list/dovecot@dovecot.org/message/Q6HI… [2] https://doc.dovecot.org/2.4.3/core/config/mail_location.html#mail_inbox_path [3] https://doc.dovecot.org/2.4.3/installation/upgrade/2.3-to-2.4.html -- T H E A N A L Y S I S A N D S O L U T I O N S C O M P A N Y Designing transportation systems everyone can use https://www.AnalysisAndSolutions.com/

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