The IAX2 channel driver (chan_iax2) in Asterisk before 1.2.22 and 1.4.x before 1.4.8, Business Edition before B.2.2.1, AsteriskNOW before beta7, Appliance Developer Kit before 0.5.0, and s800i before 1.0.2 allows remote attackers to cause a denial of service (crash) via a crafted (1) LAGRQ or (2) LAGRP frame that contains information elements of IAX frames, which results in a NULL pointer dereference when Asterisk does not properly set an associated variable.
http://www.vupen.com/english/advisories/2007/2563
http://www.securitytracker.com/id?1018407
http://www.securityfocus.com/bid/24950
http://www.novell.com/linux/security/advisories/2007_15_sr.html
http://www.debian.org/security/2007/dsa-1358
http://security.gentoo.org/glsa/glsa-200802-11.xml
http://secunia.com/advisories/29051
http://secunia.com/advisories/26099