A vulnerability in the Network Address Translation - Protocol Translation (NAT-PT) feature of Junos OS on SRX series devices may allow a certain valid IPv6 packet to crash the flowd daemon. Repeated crashes of the flowd daemon can result in an extended denial of service condition for the SRX device. Affected releases are Juniper Networks Junos OS: 12.1X46 versions prior to 12.1X46-D72; 12.3X48 versions prior to 12.3X48-D55; 15.1X49 versions prior to 15.1X49-D90.