The firewall engine in Microsoft Forefront Threat Management Gateway, Medium Business Edition (TMG MBE); and Internet Security and Acceleration (ISA) Server 2004 SP3, 2006, 2006 Supportability Update, and 2006 SP1; does not properly manage the session state of web listeners, which allows remote attackers to cause a denial of service (many stale sessions) via crafted packets, aka "Web Proxy TCP State Limited Denial of Service Vulnerability."