Cisco IOS 12.1 through 12.4, and 15.0M before 15.0(1)M1, allows remote attackers to cause a denial of service (interface queue wedge) via malformed H.323 packets, aka Bug ID CSCta19962.
http://www.vupen.com/english/advisories/2010/0706
http://www.securitytracker.com/id?1023742
http://www.cisco.com/en/US/products/products_security_advisory09186a0080b20ee4.shtml