main/rtp.c in Asterisk Open Source 1.6.1 before 1.6.1.2 allows remote attackers to cause a denial of service (crash) via an RTP text frame without a certain delimiter, which triggers a NULL pointer dereference and the subsequent calculation of an invalid pointer.
https://exchange.xforce.ibmcloud.com/vulnerabilities/52046
http://www.vupen.com/english/advisories/2009/2067
http://www.securitytracker.com/id?1022608
http://www.securityfocus.com/bid/35837
http://secunia.com/advisories/36039
http://downloads.asterisk.org/pub/security/AST-2009-004.html