Cisco VPN 3000 Concentrator 2.2.x, and 3.x before 3.5.3, adds an "HTTPS on Public Inbound (XML-Auto)(forward/in)" rule but sets the protocol to "ANY" when the XML filter configuration is enabled, which ultimately allows arbitrary traffic to pass through the concentrator.
http://www.securityfocus.com/bid/5614
http://www.iss.net/security_center/static/10023.php
http://www.cisco.com/warp/public/707/vpn3k-multiple-vuln-pub.shtml