Asterisk 1.4 before 1.4.1 and 1.2 before 1.2.16 allows remote attackers to cause a denial of service (crash) by sending a Session Initiation Protocol (SIP) packet without a URI and SIP-version header, which results in a NULL pointer dereference.
https://exchange.xforce.ibmcloud.com/vulnerabilities/32830
http://www.vupen.com/english/advisories/2007/0830
http://www.securitytracker.com/id?1017723
http://www.securityfocus.com/bid/22838
http://www.novell.com/linux/security/advisories/2007_34_asterisk.html
http://www.kb.cert.org/vuls/id/228032
http://www.debian.org/security/2007/dsa-1358
http://security.gentoo.org/glsa/glsa-200703-14.xml
http://secunia.com/advisories/25582
http://secunia.com/advisories/24578
http://secunia.com/advisories/24380
http://labs.musecurity.com/advisories/MU-200703-01.txt