Cisco VPN 3000 Concentrator 2.2.x, 3.6(Rel), and 3.x before 3.5.5, allows remote attackers to cause a denial of service via a long user name.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2002-1089
http://www.cisco.com/warp/public/707/vpn3k-multiple-vuln-pub.shtml