Dovecot Dovecot vulnerabilities

CVE-2026-42006 Medium · 4.3 CWE-400 May 12, 2026

Uncontrolled Resource Consumption in Dovecot

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. Using excessive bracing, attacker can cause memory usage up to configured memory limit. Install fixed version, or configure vsz_limit for imap process to low value. No publicly available exploits are known.

CVE-2026-40020 Medium · 4.3 CWE-284 May 12, 2026

Improper Access Control in Dovecot

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. The impact is limited to being able to spam folders to other users, no unexpected access is gained. Install to fixed version. No publicly available exploits are known.

CVE-2026-40016 Medium · 6.5 CWE-400 May 12, 2026

Uncontrolled Resource Consumption in Dovecot

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. Attacker can use this to degrade server performance and bypass configured CPU time limits for Sieve scripts. Install fixed version, or alternatively prevent direct access to Sieve scripts via ManageSieve or local access. No publicly available exploits are known.

CVE-2026-33603 Medium · 5.3 CWE-99 May 12, 2026

Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake…

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. If successful, the attacker can eavesdrop communications between Dovecot and client as MITM proxy. Install fixed version. No publicly available exploits are known.

CVE-2026-27851 Critical · 9.1 CWE-235 May 12, 2026

When safe filter is used with variable expansion, all following pipelines on the same…

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. This can enable SQL / LDAP injection attacks when used in authentication. Avoid using safe filter until on fixed version. No publicly available exploits are known.

CVE-2026-27860 Medium · 5.3 CWE-90 Mar 27, 2026

LDAP Injection in Dovecot

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.

CVE-2026-27859 Medium · 5.3 CWE-400 Mar 27, 2026

Uncontrolled Resource Consumption in Dovecot

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 exploits are known.

CVE-2026-27858 High · 7.5 CWE-400 Mar 27, 2026

Uncontrolled Resource Consumption in Dovecot

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-2026-27857 High · 7.5 CWE-400 Mar 27, 2026

Uncontrolled Resource Consumption in Dovecot

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-2026-27856 Medium · 5.9 CWE-287 Mar 27, 2026

Improper Authentication in Dovecot

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-2026-27855 Medium · 5.9 CWE-294 Mar 27, 2026

Authentication Bypass by Capture-replay in Dovecot

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-2026-24031 High · 8.2 CWE-89 Mar 27, 2026

SQL Injection in Dovecot

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.

CVE-2026-0394 Medium · 5.3 CWE-22 Mar 27, 2026

Path Traversal in Dovecot

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-2025-59032 High · 7.5 CWE-20 Mar 27, 2026

Improper Input Validation in Dovecot

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-2025-59031 Medium · 4.3 CWE-200 Mar 27, 2026

Exposure of Sensitive Information in Dovecot

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-2025-59028 High · 7.5 CWE-20 Mar 27, 2026

Improper Input Validation in Dovecot

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 exploits are known.