Heap-based buffer overflow in the TFTP server capability in Cisco IOS 11.1, 11.2, and 11.3 allows remote attackers to cause a denial of service (reset) or modify configuration via a long filename.
http://marc.info/?l=bugtraq&m=103002169829669&w=2
http://online.securityfocus.com/archive/1/284634
http://www.cisco.com/warp/public/707/ios-tftp-long-filename-pub.shtml