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 escalation in certain configurations. The documentation does not advise against the use of passdb definitions that have the same driver and args settings. One such configuration would be where an administrator wishes to use the same PAM configuration or passwd file for both normal and master users but use the username_filter setting to restrict which of the users is able to be a master user.

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.

The Sieve engine in Dovecot before 2.3.15 allows Uncontrolled Resource Consumption, as demonstrated by a situation with a complex regular expression for the regex extension.

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.

Dovecot before 2.3.13 has Improper Input Validation in lda, lmtp, and imap, leading to an application crash via a crafted email message with certain choices for ten thousand MIME parts.

An issue was discovered in Dovecot before 2.3.13. By using IMAP IDLE, an authenticated attacker can trigger unhibernation via attacker-controlled parameters, leading to access to other users' email messages (and path disclosure).

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.

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.

In Dovecot before 2.3.11.3, uncontrolled recursion in submission, lmtp, and lda allows remote attackers to cause a denial of service (resource consumption) via a crafted e-mail message with deeply nested MIME parts.

In Dovecot before 2.3.10.1, remote unauthenticated attackers can crash the lmtp or submission process by sending mail with an empty localpart.