The message parsing feature in Dovecot 1.1.4 and 1.1.5, when using the FETCH ENVELOPE command in the IMAP client, allows remote attackers to cause a denial of service (persistent crash) via an email with a malformed From address, which triggers an assertion error, aka "invalid message address parsing bug."
https://exchange.xforce.ibmcloud.com/vulnerabilities/46227
http://www.ubuntu.com/usn/usn-666-1
http://www.securityfocus.com/bid/31997
http://www.dovecot.org/list/dovecot-news/2008-October/000089.html
http://security.gentoo.org/glsa/glsa-200812-16.xml
http://secunia.com/advisories/33149