A NULL Pointer Dereference vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS allows a local, low-privileged attacker to cause a Denial-of-Service (DoS). When a specific command is executed, the pfe crashes. This will cause traffic forwarding to be interrupted until the system self-recovers. Repeated execution will create a sustained DoS condition. This issue only affects MX Series devices with Line cards MPC1-MPC9. This issue affects: Junos OS on MX Series: * All versions before 21.4R3-S9, * from 22.2 before 22.2R3-S5,  * from 22.3 before 22.3R3-S4, * from 22.4 before 22.4R3-S2, * from 23.2 before 23.2R2-S1, * from 23.4 before 23.4R2.