Dovecot is an IMAP server, written with security primarily in mind, for Linux and other UNIX-like systems. It also contains a small POP3 server. It supports mail in either of maildir or mbox formats. The SQL drivers and authentication plug-ins are provided as sub-packages.
Two flaws were found in the way some settings were enforced by the script-login functionality of Dovecot. A remote, authenticated user could use these flaws to bypass intended access restrictions or conduct a directory traversal attack by leveraging login scripts. (CVE-2011-2166, CVE-2011-2167)
A flaw was found in the way Dovecot performed remote server identity verification, when it was configured to proxy IMAP and POP3 connections to remote hosts using TLS/SSL protocols. A remote attacker could use this flaw to conduct man-in-the-middle attacks using an X.509 certificate issued by a trusted Certificate Authority (for a different name). (CVE-2011-4318)
This update also fixes the following bug:
Users of dovecot are advised to upgrade to these updated packages, which contain backported patches to correct these issues. After installing the updated packages, the dovecot service will be restarted automatically.