The IPsec module in the VPN component in Ingate Firewall before 4.6.0 and SIParator before 4.6.0 allows remote attackers to cause a denial of service (module crash) via an IPsec Phase 2 proposal that lacks Perfect Forward Secrecy (PFS).
http://www.securityfocus.com/bid/26486
http://www.ingate.com/relnote-460.php