An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, network-based attacker to cause a Denial of Service (DoS). If specific traffic is received on MX Series and its rate exceeds the respective DDoS protection limit the ingress PFE will crash and restart. Continued receipt of this traffic will create a sustained DoS condition. This issue affects Juniper Networks Junos OS on MX Series: All versions prior to 19.1R3-S10; 19.2 versions prior to 19.2R3-S7; 19.3 versions prior to 19.3R3-S8; 19.4 versions prior to 19.4R3-S11; 20.2 versions prior to 20.2R3-S5; 20.4 versions prior to 20.4R3-S6; 21.1 versions prior to 21.1R3-S5; 21.2 versions prior to 21.2R3-S4; 21.3 versions prior to 21.3R3; 21.4 versions prior to 21.4R3; 22.1 versions prior to 22.1R2.