A Missing Release of Memory after Effective Lifetime vulnerability in the Application Quality of Experience (appqoe) subsystem of the PFE of Juniper Networks Junos OS on SRX Series allows an unauthenticated network based attacker to cause a Denial of Service (DoS). Upon receiving specific traffic a memory leak will occur. Sustained processing of such specific traffic will eventually lead to an out of memory condition that prevents all services from continuing to function, and requires a manual restart to recover. A device is only vulnerable when advance(d) policy based routing (APBR) is configured and AppQoE (sla rule) is not configured for these APBR rules. This issue affects Juniper Networks Junos OS on SRX Series: 20.3 versions prior to 20.3R3-S2; 20.4 versions prior to 20.4R3-S2; 21.1 versions prior to 21.1R3; 21.2 versions prior to 21.2R2-S1, 21.2R3; 21.3 versions prior to 21.3R1-S2, 21.3R2. This issue does not affect Juniper Networks Junos OS versions prior to 20.3R1.