The L2TP packet processing functionality in Juniper Netscreen and ScreenOS Firewall products with ScreenOS before 6.3.0r13-dnd1, 6.3.0r14 through 6.3.0r18 before 6.3.0r18-dnc1, and 6.3.0r19 allows remote attackers to cause a denial of service via a crafted L2TP packet.
http://www.securitytracker.com/id/1033832
http://kb.juniper.net/InfoCenter/index?page=content&id=JSA10704