The Publish/Subscribe Framework in the PJSIP channel driver in Asterisk Open Source 12.x before 12.3.1, when sub_min_expiry is set to zero, allows remote attackers to cause a denial of service (assertion failure and crash) via an unsubscribe request when not subscribed to the device.
http://www.securityfocus.com/archive/1/532414/100/0/threaded
http://packetstormsecurity.com/files/127087/Asterisk-Project-Security-Advisory-AST-2014-005.html
http://downloads.asterisk.org/pub/security/AST-2014-005.html