Cisco IOS 12.2T, 12.3 and 12.3T, when processing an ISAKMP profile that specifies XAUTH authentication after Phase 1 negotiation, may not process certain attributes in the ISAKMP profile that specifies XAUTH, which allows remote attackers to bypass XAUTH and move to Phase 2 negotiations.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A5738
http://www.cisco.com/warp/public/707/cisco-sa-20050406-xauth.shtml