The index_get_ids function in index.c in imapd in Cyrus IMAP Server before 2.4.11, when server-side threading is enabled, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted References header in an e-mail message.
https://exchange.xforce.ibmcloud.com/vulnerabilities/69842
http://www.redhat.com/support/errata/RHSA-2011-1508.html
http://www.mandriva.com/security/advisories?name=MDVSA-2012:037
http://git.cyrusimap.org/cyrus-imapd/commit/?id=6e776956a1a9dfa58eacdd0ddd52644009eac9e5