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.