reqresp_parser.c in the SIP channel driver in Asterisk Open Source 1.8.x before 1.8.4.2 does not initialize certain strings, which allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a malformed Contact header.
https://exchange.xforce.ibmcloud.com/vulnerabilities/67812
http://www.securityfocus.com/bid/48096
http://www.securityfocus.com/archive/1/518236/100/0/threaded
http://securitytracker.com/id?1025598
http://secunia.com/advisories/44828
http://lists.fedoraproject.org/pipermail/package-announce/2011-June/062013.html
http://lists.fedoraproject.org/pipermail/package-announce/2011-July/062658.html