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://www.securityfocus.com/bid/5328
http://www.iss.net/security_center/static/9700.php
http://www.cisco.com/warp/public/707/ios-tftp-long-filename-pub.shtml