The web proxy component in Symantec Enterprise Firewall (SEF) 6.5.2 through 7.0, Raptor Firewall 6.5 and 6.5.3, VelociRaptor, and Symantec Gateway Security allow remote attackers to cause a denial of service (connection resource exhaustion) via multiple connection requests to domains whose DNS server is unresponsive or does not exist, which generates a long timeout.