A Use After Free vulnerability in the Advanced Forwarding Toolkit (AFT) manager process (aftmand) of Juniper Networks Junos OS allows an unauthenticated networked attacker to cause a kernel crash due to intensive polling of Abstracted Fabric (AF) interface statistics and thereby a Denial of Service (DoS). Continued gathering of AF interface statistics will create a sustained Denial of Service (DoS) condition. This issue affects Juniper Networks Junos OS on MX Series: 20.1 versions later than 20.1R1; 20.2 versions prior to 20.2R3-S5; 20.3 versions prior to 20.3R3-S4; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2; 21.2 versions prior to 21.2R2.