An Improper Handling of Exceptional Conditions vulnerability on specific PTX Series devices, including the PTX1000, PTX3000 (NextGen), PTX5000, PTX10002-60C, PTX10008, and PTX10016 Series, in Juniper Networks Junos OS allows an unauthenticated MPLS-based attacker to cause a Denial of Service (DoS) by triggering the dcpfe process to crash and FPC to restart. On affected PTX Series devices, processing specific MPLS packets received on an interface with multiple units configured may cause FPC to restart unexpectedly. Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects PTX Series devices utilizing specific FPCs found on PTX1000, PTX3000 (NextGen), PTX5000, PTX10002-60C, PTX10008, and PTX10016 Series devices, only if multiple units are configured on the ingress interface, and at least one unit has 'family mpls' *not* configured. See the configuration sample below for more information. No other platforms are affected by this vulnerability. This issue affects: Juniper Networks Junos OS on PTX Series: All versions prior to 19.1R3-S9; 19.2 versions prior to 19.2R3-S6; 19.3 versions prior to 19.3R3-S6; 19.4 versions prior to 19.4R3-S8; 20.1 versions prior to 20.1R3-S4; 20.2 versions prior to 20.2R3-S5; 20.3 versions prior to 20.3R3-S4; 20.4 versions prior to 20.4R3-S4; 21.1 versions prior to 21.1R3-S2; 21.2 versions prior to 21.2R3-S1; 21.3 versions prior to 21.3R3; 21.4 versions prior to 21.4R2; 22.1 versions prior to 22.1R2.