The Data-link Switching (DLSw) feature in Cisco IOS 11.0 through 12.4 allows remote attackers to cause a denial of service (device reload) via "an invalid value in a DLSw message... during the capabilities exchange."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5714
http://www.vupen.com/english/advisories/2007/0139
http://www.securityfocus.com/bid/21990
http://www.cisco.com/warp/public/707/cisco-sa-20070110-dlsw.shtml
http://securitytracker.com/id?1017498