Nokia Firewall Appliances running IPSO 3.3 and VPN-1/FireWall-1 4.1 Service Pack 3, IPSO 3.4 and VPN-1/FireWall-1 4.1 Service Pack 4, and IPSO 3.4 or IPSO 3.4.1 and VPN-1/FireWall-1 4.1 Service Pack 5, when SYN Defender is configured in Active Gateway mode, does not properly rewrite the third packet of a TCP three-way handshake to use the NAT IP address, which allows remote attackers to gain sensitive information.