Cisco IOS 12.0 through 12.4 on Gigabit Switch Router (GSR) devices (aka 12000 Series routers) allows remote attackers to cause a denial of service (device crash) via a malformed Protocol Independent Multicast (PIM) packet.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5477
http://www.vupen.com/english/advisories/2008/2670
http://www.securityfocus.com/bid/31356
http://www.cisco.com/en/US/products/products_security_advisory09186a0080a01491.shtml
http://tools.cisco.com/security/center/viewAlert.x?alertId=16638