dovecot is vulnerable to man-in-the-middle. 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).
hg.dovecot.org/dovecot-2.0/rev/5e9eaf63a6b1
rhn.redhat.com/errata/RHSA-2013-0520.html
secunia.com/advisories/46886
secunia.com/advisories/52311
www.dovecot.org/list/dovecot-news/2011-November/000200.html
www.openwall.com/lists/oss-security/2011/11/18/5
www.openwall.com/lists/oss-security/2011/11/18/7
access.redhat.com/security/updates/classification/#low
bugs.gentoo.org/show_bug.cgi?id=390887
bugzilla.redhat.com/show_bug.cgi?id=754980
rhn.redhat.com/errata/RHSA-2013-0520.html