CVE-2026-27857

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. 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. Install fixed version, there is no other remediation. No publicly available exploits are known.

Dovecot is an IMAP server for Linux/UNIX-like systemsa wrapper package that will just handle common things for all versioned dovecot packages.

Security Fix(es):

Dovecot has provided a script to use for attachment to text conversion. This script unsafely handles zip-style attachments. Attacker can use specially crafted OOXML documents to cause unintended files on the system to be indexed and subsequently ending up in FTS indexes. Do not use the provided script, instead, use something else like FTS tika. No publicly available exploits are known.(CVE-2025-59031)

ManageSieve AUTHENTICATE command crashes when using literal as SASL initial response. This can be used to crash ManageSieve service repeatedly, making it unavailable for other users. Control access to ManageSieve port, or disable the service if it's not needed. Alternatively upgrade to a fixed version. No publicly available exploits are known.(CVE-2025-59032)

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. 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. 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. No publicly available exploits are known.(CVE-2026-0394)

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. An attacker able to observe an OTP exchange is able to log in as the user. If authentication happens over unsecure connection, switch to SCRAM protocol. Alternatively ensure the communcations are secured, and if possible switch to OAUTH2 or SCRAM. No publicly available exploits are known.(CVE-2026-27855)

Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An attacker can use this to determine the configured credentials. Figuring out the credential will lead into full access to the affected component. Limit access to the doveadm http service port, install fixed version. No publicly available exploits are known.(CVE-2026-27856)

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. 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. Install fixed version, there is no other remediation. No publicly available exploits are known.(CVE-2026-27857)

Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory. Attacker can force managesieve-login to be unavailable by repeatedly crashing the process. Protect access to managesieve protocol, or install fixed version. No publicly available exploits are known.(CVE-2026-27858)

A mail message containing excessive amount of RFC 2231 MIME parameters causes LMTP to use too much CPU. A suitably formatted mail message causes mail delivery process to consume large amounts of CPU time. Use MTA capabilities to limit RFC 2231…

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)

• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)

• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)

• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)

• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)

• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)

• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)

• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)

• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)

• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)

• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

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. 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. Install fixed version, there is no other remediation. No publicly available exploits are known.

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)
• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)
• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)
• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)
• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)
• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)
• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)
• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)
• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Dovecot is an IMAP server for Linux and other UNIX-like systems, written primarily with security in mind. It also contains a small POP3 server, and supports e-mail in either the maildir or mbox format. The SQL drivers and authentication plug-ins are provided as subpackages.

Security Fix(es):

• dovecot: ManageSieve: Denial of Service via crafted SASL initial response in AUTHENTICATE command (CVE-2025-59032)
• dovecot: denial of service via crafted message before authentication (CVE-2026-27858)
• dovecot: denial of service via specially crafted NOOP command (CVE-2026-27857)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

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. 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. Install fixed version, there is no other remediation. No publicly available exploits are known.

• CVE-2026-27857: limit the number of open IMAP parser lists in imap-login to prevent excessive memory usage from deeply nested parentheses (e.g. NOOP (((...))))

• CVE-2026-27857: limit the number of open IMAP parser lists in imap-login to prevent excessive memory usage from deeply nested parentheses (e.g. NOOP (((...))))

• CVE-2026-27857: limit the number of open IMAP parser lists in imap-login to prevent excessive memory usage from deeply nested parentheses (e.g. NOOP (((...))))

• CVE-2026-27857: limit number of open IMAP parser lists in imap-login to prevent excessive memory usage DoS via deeply-nested parentheses

• CVE-2026-27855: fix OTP authentication replay attack via auth cache
• CVE-2026-27856: fix doveadm credential timing oracle
• CVE-2026-27857: fix excessive memory usage from deeply nested IMAP command lists (pre-auth ID command)

• CVE-2026-27857: fix excessive memory usage from many '(' in IMAP commands

• CVE-2026-27857: imap-login: limit IMAP parser open lists to prevent excessive memory usage

• CVE-2026-27857: imap-login: limit IMAP parser open lists to prevent excessive memory usage

• SECURITY UPDATE: imap-login excessive memory usage DoS (ELSCVE-123445)
  • debian/patches/CVE-2026-27857.patch: limit IMAP parser open list count via new imap_parser_params struct; cap pre-auth IMAP_LOGIN_LIST_COUNT_LIMIT to 1. Squashes upstream commits 825bc297, d0f67b52, af1fb4da, 3435e0d44.
  • CVE-2026-27857

• CVE-2026-27857: improve fix by enforcing list_count_limit on '(' (open_list) instead of ')' (close_list); the previous fix did not actually limit memory growth from many '(' characters

• CVE-2026-42006: lib-imap: fix list_count_limit to actually count open '(' instead of close ')', preventing an imap-login memory-exhaustion DoS that bypassed the CVE-2026-27857 fix

• CVE-2026-42006: lib-imap: fix list_count_limit to actually count open '(' instead of close ')', preventing an imap-login memory-exhaustion DoS that bypassed the CVE-2026-27857 fix

• CVE-2026-40020: imap-acl: reject CR/LF/control-char and non-UTF-8 injection in SETACL identifier
• CVE-2026-42006: lib-imap: fix list_count_limit to actually bound '(' (incomplete fix for CVE-2026-27857)
• CVE-2026-40016: lib-sieve: enforce sieve_max_cpu_time inside :contains/:matches matcher loops

• CVE-2026-40020: imap-acl: reject CR/LF injection in SETACL identifier
• CVE-2026-42006: lib-imap: fix list_count_limit to actually limit '(' (incomplete fix for CVE-2026-27857)
• CVE-2026-33603: login-common: reject non-base64 SASL responses to prevent SCRAM channel binding bypass
• CVE-2026-40016: lib-sieve: enforce sieve_max_cpu_time inside :contains/:matches matcher loops

• SECURITY UPDATE: imap-login excessive memory usage DoS via too many '(' in IMAP list (ELSCVE-127370)
  • debian/patches/CVE-2026-42006.patch: move list_count_limit check and counter increment into imap_parser_open_list() so '(' is what is actually bounded (the previous CVE-2026-27857 fix only limited ')'). Backport of upstream commit da1438c76b797f.
  • CVE-2026-42006

These are all security issues fixed in the dovecot24-2.4.3-1.1 package on the GA media of openSUSE Tumbleweed.

This update for dovecot24 fixes the following issues:

• Update to v2.4.3
• CVE-2025-59028: Invalid base64 authentication can cause DoS for other logins (bsc#1260894).
• CVE-2025-59031: decode2text.sh OOXML extraction may follow symlinks and read unintended files during indexing (bsc#1260895).
• CVE-2025-59032: pigeonhole: ManageSieve panic occurs with sieve-connect as a client (bsc#1260902).
• CVE-2026-24031: SQL injection possible if auth_username_chars is configured empty. Fixed escaping to always happen. v2.4 regression (bsc#1260896).
• CVE-2026-27855: OTP driver vulnerable to replay attack (bsc#1260900).
• CVE-2026-27856: Doveadm credentials were not checked using timing-safe checking function (bsc#1260899).
• CVE-2026-27857: sending excessive parenthesis causes imap-login to use excessive memory (bsc#1260898).
• CVE-2026-27858: pigeonhole: managesieve-login can allocate large amount of memory during authentication (bsc#1260901).
• CVE-2026-27859: excessive RFC 2231 MIME parameters in email would can excessive CPU usage (bsc#1260897).
• CVE-2026-27860: LDAP query injection possible if auth_username_chars is configured empty. Fixed escaping to always happen. v2.4 regression (bsc#1260893).

This update for dovecot22 fixes the following issues:

• CVE-2025-59031: decode2text.sh OOXML extraction may follow symlinks and read unintended files during indexing (bsc#1260895).
• CVE-2025-59032: pigeonhole: ManageSieve panic occurs with sieve-connect as a client (bsc#1260902).
• CVE-2026-27855: OTP driver vulnerable to replay attack (bsc#1260900).
• CVE-2026-27856: Doveadm credentials were not checked using timing-safe checking function (bsc#1260899).
• CVE-2026-27857: sending excessive parenthesis causes imap-login to use excessive memory (bsc#1260898).
• CVE-2026-27858: pigeonhole: managesieve-login can allocate large amount of memory during authentication (bsc#1260901).
• CVE-2026-27859: excessive RFC 2231 MIME parameters in email would can excessive CPU usage (bsc#1260897).

This update for dovecot24 fixes the following issues:

• Update to v2.4.3
• CVE-2025-59028: Invalid base64 authentication can cause DoS for other logins (bsc#1260894).
• CVE-2025-59031: decode2text.sh OOXML extraction may follow symlinks and read unintended files during indexing (bsc#1260895).
• CVE-2025-59032: pigeonhole: ManageSieve panic occurs with sieve-connect as a client (bsc#1260902).
• CVE-2026-24031: SQL injection possible if auth_username_chars is configured empty. Fixed escaping to always happen. v2.4 regression (bsc#1260896).
• CVE-2026-27855: OTP driver vulnerable to replay attack (bsc#1260900).
• CVE-2026-27856: Doveadm credentials were not checked using timing-safe checking function (bsc#1260899).
• CVE-2026-27857: sending excessive parenthesis causes imap-login to use excessive memory (bsc#1260898).
• CVE-2026-27858: pigeonhole: managesieve-login can allocate large amount of memory during authentication (bsc#1260901).
• CVE-2026-27859: excessive RFC 2231 MIME parameters in email would can excessive CPU usage (bsc#1260897).
• CVE-2026-27860: LDAP query injection possible if auth_username_chars is configured empty. Fixed escaping to always happen. v2.4 regression (bsc#1260893).

This update for dovecot23 fixes the following issues:

• CVE-2024-23184: parsing of messages containing many address headers (From, To, Cc, Bcc, etc.) could be excessively CPU intensive (bsc#1229184).
• CVE-2024-23185: large headers can cause resource exhaustion when parsing message (bsc#1229183).
• CVE-2025-59028: Invalid base64 authentication can cause DoS for other logins (bsc#1260894).
• CVE-2025-59031: decode2text.sh OOXML extraction may follow symlinks and read unintended files during indexing (bsc#1260895).
• CVE-2025-59032: pigeonhole: ManageSieve panic occurs with sieve-connect as a client (bsc#1260902).
• CVE-2026-27852: DoS by sending mail with bad header (bsc#1276799).
• CVE-2026-27855: OTP driver vulnerable to replay attack (bsc#1260900).
• CVE-2026-27856: Doveadm credentials were not checked using timing-safe checking function (bsc#1260899).
• CVE-2026-27857: sending excessive parenthesis causes imap-login to use excessive memory (bsc#1260898).
• CVE-2026-27858: pigeonhole: managesieve-login can allocate large amount of memory during authentication (bsc#1260901).
• CVE-2026-27859: excessive RFC 2231 MIME parameters in email would can excessive CPU usage (bsc#1260897).
• CVE-2026-33263: submission-login: Panic when mail_max_userip_connections is reached (bsc#1276794).
• CVE-2026-33603: login: base64 input can contain tabs that bypass IPC protection (bsc#1265147).
• CVE-2026-33604: SMTP Smuggling via Missing Dot-Stuffing (bsc#1276802).
• CVE-2026-33605: managesieve-login: Pre-auth crash (bsc#1276809).
• CVE-2026-33606: dsync: Mail content can cause dsync protocol injection (bsc#1276800).
• CVE-2026-33607: IMAP LIST match_sub() Exponential Backtracking -- CPU Denial of Service (bsc#1276795).
• CVE-2026-40014: CPU DoS via Crafted References Header (bsc#1276804).
• CVE-2026-40015: imap-hibernate can be crashed (bsc#1276812).
• CVE-2026-40016: Sieve :contains/:matches O(NxM) substring match bypasses sieve_max_cpu_time limit (bsc#1265148).
• CVE-2026-40019: managesieve-login pre-auth infinite loop (bsc#1276811).
• CVE-2026-40020: IMAP folders can be shared-spammed to everyone (bsc#1265149).
• CVE-2026-40203: IMAP Compression Can Reveal Whether a Small Synced Email Body Matches Sender-Chosen Text (bsc#1276815).
• CVE-2026-40205: OAuth2 passdb scope enforcement bypass via OR semantics in remote validation path (bsc#1276820).
• CVE-2026-42006: imap-login: uncontrolled memory usage with excessive bracing over IMAP (bsc#1265150).
• CVE-2026-42007: editheader RCE (bsc#1276817).
• CVE-2026-42008: XCLIENT FORWARD= bare token not namespaced (bsc#1276824).
• CVE-2026-42391: imap: Pre-login memory/CPU growth with ID command (bsc#1276835).
• CVE-2026-42393: doveadm_password or api key length can still be leaked with timing comparisons (bsc#1276827).
• CVE-2026-42395: Single NUL-Byte XCLIENT FORWARD Payload Crashes (bsc#1276826).
• CVE-2026-52681: Sieve resource usage tracking lost when active script changes (bsc#1276828).
• CVE-2026-52687: IMAP: COMPRESS ZSTD can cause excessive memory usage (bsc#1276837).
• CVE-2026-73208: auth: db-oauth2: aud claim used as fallback for missing scope claim (bsc#1276830).
• CVE-2026-73209: imap-login crash: Self-recursion on zero-output decompress chunks (bsc#1276833).

Changes for dovecot23:

• Update to version 2.3.21.1.