Asterisk Open Source 1.8.x, 11.x before 11.21.1, 12.x, and 13.x before 13.7.1 and Certified Asterisk 1.8.28, 11.6 before 11.6-cert12, and 13.1 before 13.1-cert3 allow remote authenticated users to cause a denial of service (uninitialized pointer dereference and crash) via a zero length error correcting redundancy packet for a UDPTL FAX packet that is lost.
http://www.securitytracker.com/id/1034931
http://www.debian.org/security/2016/dsa-3700
http://downloads.asterisk.org/pub/security/AST-2016-003.html