In Dovecot before 2.2.36.3 and 2.3.x before 2.3.5.1, a local attacker can cause a buffer overflow in the indexer-worker process, which can be used to elevate to root. This occurs because of missing checks in the fts and pop3-uidl components.

It was discovered that Dovecot before versions 2.2.36.1 and 2.3.4.1 incorrectly handled client certificates. A remote attacker in possession of a valid certificate with an empty username field could possibly use this issue to impersonate other users.

Dovecot before version 2.2.29 is vulnerable to a denial of service. When 'dict' passdb and userdb were used for user authentication, the username sent by the IMAP/POP3 client was sent through var_expand() to perform %variable expansion. Sending specially crafted %variable fields could result in excessive memory usage causing the process to crash (and restart), or excessive CPU usage causing all authentications to hang.

A specially crafted email delivered over SMTP and passed on to Dovecot by MTA can trigger an out of bounds read resulting in potential sensitive information disclosure and denial of service. In order to trigger this vulnerability, an attacker needs to send a specially crafted email message to the server.

A denial of service flaw was found in dovecot before 2.2.34. An attacker able to generate random SNI server names could exploit TLS SNI configuration lookups, leading to excessive memory usage and the process to restart.

A flaw was found in dovecot 2.0 up to 2.2.33 and 2.3.0. An abort of SASL authentication results in a memory leak in dovecot's auth client used by login processes. The leak has impact in high performance configuration where same login processes are reused and can cause the process to crash due to memory exhaustion.

The ssl-proxy-openssl.c function in Dovecot before 2.2.17, when SSLv3 is disabled, allow remote attackers to cause a denial of service (login process crash) via vectors related to handshake failures.

The auth component in Dovecot before 2.2.27, when auth-policy is configured, allows a remote attackers to cause a denial of service (crash) by aborting authentication without setting a username.

The IMAP functionality in Dovecot before 2.2.2 allows remote attackers to cause a denial of service (infinite loop and CPU consumption) via invalid APPEND parameters.

Dovecot 1.1 before 2.2.13 and dovecot-ee before 2.1.7.7 and 2.2.x before 2.2.12.12 does not properly close old connections, which allows remote attackers to cause a denial of service (resource consumption) via an incomplete SSL/TLS handshake for an IMAP/POP3 connection.