The data-link switching (DLSw) component in Cisco IOS 12.0 through 12.4 allows remote attackers to cause a denial of service (device restart or memory consumption) via crafted (1) UDP port 2067 or (2) IP protocol 91 packets.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5821
https://exchange.xforce.ibmcloud.com/vulnerabilities/41482
http://www.vupen.com/english/advisories/2008/1006/references
http://www.us-cert.gov/cas/techalerts/TA08-087B.html
http://www.securitytracker.com/id?1019712
http://www.securityfocus.com/bid/28465
http://www.cisco.com/en/US/products/products_security_advisory09186a0080969866.shtml