An Unchecked Input for Loop Condition vulnerability in a NAT library of Juniper Networks Junos OS allows a local authenticated attacker with low privileges to cause a Denial of Service (DoS). When an inconsistent "deterministic NAT" configuration is present on an SRX, or MX with SPC3 and then a specific CLI command is issued the SPC will crash and restart. Repeated execution of this command will lead to a sustained DoS. Such a configuration is characterized by the total number of port blocks being greater than the total number of hosts. An example for such configuration is: [ services nat source pool TEST-POOL address x.x.x.0/32 to x.x.x.15/32 ] [ services nat source pool TEST-POOL port deterministic block-size 1008 ] [ services nat source pool TEST-POOL port deterministic host address y.y.y.0/24] [ services nat source pool TEST-POOL port deterministic include-boundary-addresses] where according to the following calculation: 65536-1024=64512 (number of usable ports per IP address, imp…