The IAX2 protocol implementation in Asterisk Open Source 1.0.x, 1.2.x before 1.2.30, and 1.4.x before 1.4.21.2; Business Edition A.x.x, B.x.x before B.2.5.4, and C.x.x before C.1.10.3; AsteriskNOW; Appliance Developer Kit 0.x.x; and s800i 1.0.x before 1.2.0.1 allows remote attackers to cause a denial of service (call-number exhaustion and CPU consumption) by quickly sending a large number of IAX2 (IAX) POKE requests.
https://www.redhat.com/archives/fedora-package-announce/2008-July/msg00839.html
https://exchange.xforce.ibmcloud.com/vulnerabilities/43942
http://www.vupen.com/english/advisories/2008/2168/references
http://www.securitytracker.com/id?1020535
http://www.securityfocus.com/archive/1/494675/100/0/threaded
http://security.gentoo.org/glsa/glsa-200905-01.xml
http://secunia.com/advisories/34982
http://secunia.com/advisories/31194