Juniper Junos 11.4 before 11.4R12, 12.1X44 before 12.1X44-D32, 12.1X45 before 12.1X45-D25, 12.1X46 before 12.1X46-D20, and 12.1X47 before 12.1X47-D10 on SRX Series devices, when NAT protocol translation from IPv4 to IPv6 is enabled, allows remote attackers to cause a denial of service (flowd hang or crash) via a crafted packet.