Cisco IOS 12.1, 12.2, 12.3, and 12.4, with IPv4 UDP services and the IPv6 protocol enabled, allows remote attackers to cause a denial of service (device crash and possible blocked interface) via a crafted IPv6 packet to the device.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5860
https://exchange.xforce.ibmcloud.com/vulnerabilities/41475
http://www.vupen.com/english/advisories/2008/1006/references
http://www.us-cert.gov/cas/techalerts/TA08-087B.html
http://www.securitytracker.com/id?1019713
http://www.securityfocus.com/bid/28461