Debian Dovecot vulnerabilities

CVE-2026-27858 [HIGH] CVE-2026-27858: dovecot - Attacker can send a specifically crafted message before authentication that caus... 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. Scope: local bookworm: resolved (fixed

CVE-2026-27856 [HIGH] CVE-2026-27856: dovecot - Doveadm credentials are verified using direct comparison which is susceptible to... 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. Scope

CVE-2026-0394 [MEDIUM] CVE-2026-0394: dovecot - When dovecot has been configured to use per-domain passwd files, and they are pl... 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

CVE-2026-27855 [MEDIUM] CVE-2026-27855: dovecot - Dovecot OTP authentication is vulnerable to replay attack under specific conditi... 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.

CVE-2026-27857 [MEDIUM] CVE-2026-27857: dovecot - Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1M... 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, whic

CVE-2026-27859 [MEDIUM] CVE-2026-27859: dovecot - A mail message containing excessive amount of RFC 2231 MIME parameters causes LM... 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 MIME parameters in mail messages, or upgrade to fixed version where the processing is limited. No publicly available explo

CVE-2026-24031 [HIGH] CVE-2026-24031: dovecot - Dovecot SQL based authentication can be bypassed when auth_username_chars is cle... Dovecot SQL based authentication can be bypassed when auth_username_chars is cleared by admin. This vulnerability allows bypassing authentication for any user and user enumeration. Do not clear auth_username_chars. If this is not possible, install latest fixed version. No publicly available exploits are known. Scope: local bookworm: resolved bullseye: resolved forky

CVE-2026-27860 [LOW] CVE-2026-27860: dovecot - If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter ... If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authentication. This leads to potentially bypassing restrictions and allows probing of LDAP structure. Do not clear out auth_username_chars, or install fixed version. No publicly available exploits are known. Scope: local bookworm: resolved bullseye: resolved forky: open

CVE-2025-59032 [HIGH] CVE-2025-59032: dovecot - ManageSieve AUTHENTICATE command crashes when using literal as SASL initial resp... 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. Scope: local bookworm:

CVE-2025-59031 [MEDIUM] CVE-2025-59031: dovecot - Dovecot has provided a script to use for attachment to text conversion. This scr... 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 availab

CVE-2025-59028 [MEDIUM] CVE-2025-59028: dovecot - When sending invalid base64 SASL data, login process is disconnected from the au... When sending invalid base64 SASL data, login process is disconnected from the auth server, causing all active authentication sessions to fail. Invalid BASE64 data can be used to DoS a vulnerable server to break concurrent logins. Install fixed version or disable concurrency in login processes (heavy perfomance penalty on large deployments). No publicly available e

CVE-2025-30189 [HIGH] CVE-2025-30189: dovecot - When cache is enabled, some passdb/userdb drivers incorrectly cache all users wi... 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. After cached login, all subsequent logins are for same user. Install fixed version or disable caching either globally or for the impacted passdb/userdb drivers. No publicly available exploits are known. Scope

CVE-2024-23185 [HIGH] CVE-2024-23185: dovecot - Very large headers can cause resource exhaustion when parsing message. The messa... Very large headers can cause resource exhaustion when parsing message. The message-parser normally reads reasonably sized chunks of the message. However, when it feeds them to message-header-parser, it starts building up "full_value" buffer out of the smaller chunks. The full_value buffer has no size limit, so large headers can cause large memory usage. It doesn't m

CVE-2024-23184 [MEDIUM] CVE-2024-23184: dovecot - Having a large number of address headers (From, To, Cc, Bcc, etc.) becomes exces... Having a large number of address headers (From, To, Cc, Bcc, etc.) becomes excessively CPU intensive. With 100k header lines CPU usage is already 12 seconds, and in a production environment we observed 500k header lines taking 18 minutes to parse. Since this can be triggered by external actors sending emails to a victim, this is a security issue. An external attac

CVE-2022-30550 [HIGH] CVE-2022-30550: dovecot - An issue was discovered in the auth component in Dovecot 2.2 and 2.3 before 2.3.... An issue was discovered in the auth component in Dovecot 2.2 and 2.3 before 2.3.20. When two passdb configuration entries exist with the same driver and args settings, incorrect username_filter and mechanism settings can be applied to passdb definitions. These incorrectly applied settings can lead to an unintended security configuration and can permit privilege esca

CVE-2021-29157 [HIGH] CVE-2021-29157: dovecot - Dovecot before 2.3.15 allows ../ Path Traversal. An attacker with access to the ... Dovecot before 2.3.15 allows ../ Path Traversal. An attacker with access to the local filesystem can trick OAuth2 authentication into using an HS256 validation key from an attacker-controlled location. This occurs during use of local JWT validation with the posix fs driver. Scope: local bookworm: resolved (fixed in 1:2.3.13+dfsg1-2) bullseye: resolved (fixed in 1:2.

CVE-2021-33515 [MEDIUM] CVE-2021-33515: dovecot - The submission service in Dovecot before 2.3.15 allows STARTTLS command injectio... The submission service in Dovecot before 2.3.15 allows STARTTLS command injection in lib-smtp. Sensitive information can be redirected to an attacker-controlled address. Scope: local bookworm: resolved (fixed in 1:2.3.13+dfsg1-2) bullseye: resolved (fixed in 1:2.3.13+dfsg1-2) forky: resolved (fixed in 1:2.3.13+dfsg1-2) sid: resolved (fixed in 1:2.3.13+dfsg1-2) tri

CVE-2020-12674 [HIGH] CVE-2020-12674: dovecot - In Dovecot before 2.3.11.3, sending a specially formatted RPA request will crash... In Dovecot before 2.3.11.3, sending a specially formatted RPA request will crash the auth service because a length of zero is mishandled. Scope: local bookworm: resolved (fixed in 1:2.3.11.3+dfsg1-1) bullseye: resolved (fixed in 1:2.3.11.3+dfsg1-1) forky: resolved (fixed in 1:2.3.11.3+dfsg1-1) sid: resolved (fixed in 1:2.3.11.3+dfsg1-1) trixie: resolved (fixed in 1:

CVE-2020-10957 [HIGH] CVE-2020-10957: dovecot - In Dovecot before 2.3.10.1, unauthenticated sending of malformed parameters to a... In Dovecot before 2.3.10.1, unauthenticated sending of malformed parameters to a NOOP command causes a NULL Pointer Dereference and crash in submission-login, submission, or lmtp. Scope: local bookworm: resolved (fixed in 1:2.3.10.1+dfsg1-1) bullseye: resolved (fixed in 1:2.3.10.1+dfsg1-1) forky: resolved (fixed in 1:2.3.10.1+dfsg1-1) sid: resolved (fixed in 1:2.3.1

CVE-2020-12673 [HIGH] CVE-2020-12673: dovecot - In Dovecot before 2.3.11.3, sending a specially formatted NTLM request will cras... In Dovecot before 2.3.11.3, sending a specially formatted NTLM request will crash the auth service because of an out-of-bounds read. Scope: local bookworm: resolved (fixed in 1:2.3.11.3+dfsg1-1) bullseye: resolved (fixed in 1:2.3.11.3+dfsg1-1) forky: resolved (fixed in 1:2.3.11.3+dfsg1-1) sid: resolved (fixed in 1:2.3.11.3+dfsg1-1) trixie: resolved (fixed in 1:2.3.1