- dovecot - dovecot.org

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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Confusion about ldap in 2.4
by fc26wuqa＠studserv.uni-leipzig.de 28 Apr '26

28 Apr '26

Hello, With dovecot 2.3 it was clear to me, how I should set up ldap: Include `conf.d/auth-ldap.conf.ext` in `conf.d/10-auth.conf` and include `dovecot-ldap.conf.ext` with the usual parameters like hosts, uris, dn, etc. In dovecot 2.4 I am a little bit confused about whats the best practice. I heard about that .ext files being outdated and examples in the documentation saying I should put everything in dovecot.conf? So If in 2.3 my config would look like this: ``` # auth-ldap.conf.ext passdb { driver = ldap args = /etc/dovecot/dovecot-ldap.conf.ext } userdb { driver = ldap args = /etc/dovecot/dovecot-ldap.conf.ext } ``` ``` # dovecot-ldap.conf.ext hosts = ldap.something.org:636 uris = ldaps://smoething.org dn = cn=something,ou=something,dc=something,dc=org dnspass = somethingsomething auth_bind = yes auth_bind_userdn = uid=%u,ou=something ... ``` I would put something like this in dovecot.conf? Or in auth-ldap.conf.ext? ``` ldap_uris = ldap://ldap.example.org ldap_auth_dn = cn=admin,dc=example,dc=org ldap_auth_dn_password = secret ldap_base = dc=example,dc=org passdb ldap { bind = yes filter = (&(objectClass=posixAccount)(uid=%{user})) fields { user = %{ldap:uid} } } ``` (https://doc.dovecot.org/2.4.3/core/config/auth/databases/ldap.html#dn-lookup)

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Upgrading from 2.4.2 to 2.4.3 broke static password login
by harrison＠hhj.me 28 Apr '26

28 Apr '26

Hey folks, I've got dovecot running via docker on version 2.4.2. Here's what my config extension looks like: ``` # auth_mechanisms = plain login auth_verbose = yes passdb static { password = %{env:USER_PASSWORD} } service lmtp { inet_listener lmtps { port = 31024 ssl = no } } ssl_server_cert_file = /etc/dovecot/ssl/cert.pem ssl_server_key_file = /etc/dovecot/ssl/key.pem ssl = yes auth_allow_cleartext = no namespace inbox { type = private separator = / inbox = yes mailbox Drafts { special_use = \Drafts auto = subscribe } mailbox Junk { special_use = \Junk auto = create } mailbox spam { special_use = \Junk auto = no } mailbox Spam { special_use = \Junk auto = no } mailbox Trash { special_use = \Trash auto = subscribe } mailbox TRASH { special_use = \Trash auto = no } mailbox Sent { special_use = \Sent auto = subscribe } mailbox "Sent Mail" { special_use = \Sent auto = no } mailbox "Sent Messages" { special_use = \Sent auto = no } mailbox Archive { special_use = \Archive auto = create } mailbox "Archives" { special_use = \Archive auto = no } } ``` I have env `USER_PASSWORD` defined in the format of `{PLAIN}REDACTED` This has been humming along fine for a little while. I recently automatically upgraded to 2.4.3 which broke my ability to login via IMAP to retrieve emails (it also broke my local mail transport setup; it was unable to send emails). I could see the following messages in the logs: ``` Apr 27 11:12:09 auth(REDACTED,REDACTED,sasl:plain)<REDACTED>: Info: static: No password returned (and no nopassword) Apr 27 11:12:11 imap-login: Info: Login aborted: Connection closed (auth failed, 1 attempts in 6 secs) (auth_failed): user=<REDACTED>, method=PLAIN, rip=REDACTED, lip=172.17.0.2, TLS, session=<REDACTED> ``` Downgrading back to 2.4.2 "fixed" the problem (I was able to login again; LMTP worked again). I didn't change my config extension between the upgrades. I tried searching https://github.com/search?q=repo%3Adovecot%2Fcore+password&type=issues and I see a few related to passwords but nothing is really jumping out at me. Help? I'm staying pinned on 2.4.2 for now but that's not a long term solution.

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Panic in logs
by Kamil Jońca 26 Apr '26

26 Apr '26

Recently I found in my lda logs: 2025-12-30T07:55:14.717927+01:00 alfa dovecot: lda(kjonca): Error: Raw backtrace: #1 [unw_get_proc_name() failed: -10] -> #2 i_syslog_fatal_handler[0x7f99a2351430] -> #3 i_panic[0x7f99a226d453] -> #4 [unw_get_proc_name() failed: -10] -> #5 [unw_get_proc_name() failed: -10] -> #6 [unw_get_proc_name() failed: -10] -> #7 buffer_append[0x7f99a2345270] -> #8 dregex_code_match_groups[0x7f99a233f1a0] -> #9 [unw_get_proc_name() failed: -10] -> #10 [unw_get_proc_name() failed: -10] -> #11 sieve_match_value[0x7f99a117f770] -> #12 sieve_match[0x7f99a117fa30] -> #13 [unw_get_proc_name() failed: -10] -> #14 sieve_interpreter_continue[0x7f99a117e100] -> #15 sieve_multiscript_run[0x7f99a1190330] -> #16 [unw_get_proc_name() failed: -10] -> #17 mail_deliver[0x7f99a27e54a0] -> #18 main[0x55e371c555e0] -> #19 __libc_start_call_main[0x7f99a1e29f00] -> #20 __libc_start_main_alias_2[0x7f99a1e29fa0] -> #21 _start[0x55e371c566a0] And sadly it seems, that mail is missing (it was passed to pipe program to further processing) KJ -- http://wolnelektury.pl/wesprzyj/teraz/ When you go out to buy, don't show your silver.

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Incorrect ARC signature on emails
by Lafiel Elentari 25 Apr '26

25 Apr '26

Hello. On the mail server, I configured addition of the `Authentication-Results` header with authentication check results. I noticed that emails from the dovecot.org server have an incorrect ARC signature: Authentication-Results: ...; dkim=pass header.d=dovecot.org header.s=... header.b=...; dkim=fail ("body hash did not verify") header.d=... header.s=... header.b=...; arc=reject ("signature check failed: fail, {[1] = sig:dovecot.org:reject}"); spf=pass (...: domain of "dovecot-bounces+...=...(a)dovecot.org" designates ... as permitted sender) smtp.mailfrom="dovecot-bounces+...=...(a)dovecot.org"; dmarc=pass (policy=reject) header.from=dovecot.org ``` -- Best regards, Lafiel Elentari mailto:lafiel@elven.pw

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