Cisco IOS 12.2T through 12.4 allows remote attackers to bypass Authentication, Authorization, and Accounting (AAA) RADIUS authentication, if the fallback method is set to none, via a long username.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5756
https://exchange.xforce.ibmcloud.com/vulnerabilities/21190
http://www.securitytracker.com/alerts/2005/Jun/1014330.html
http://www.cisco.com/warp/public/707/cisco-sa-20050629-aaa.shtml