An Improper Handling of Exceptional Conditions vulnerability in the Packet Forwarding Engine (pfe) of the Juniper Networks Junos OS Evolved on ACX Series devices allows an unauthenticated, network based attacker sending specific transit protocol traffic to cause a partial Denial of Service (DoS) to downstream devices. Receipt of specific transit protocol packets is incorrectly processed by the Routing Engine (RE), filling up the DDoS protection queue which is shared between routing protocols. This influx of transit protocol packets causes DDoS protection violations, resulting in protocol flaps which can affect connectivity to networking devices. This issue affects both IPv4 and IPv6. This issue does not require any specific routing protocol to be configured or enabled. The following commands can be used to monitor the DDoS protection queue:        labuser@re0> show evo-pfemand host pkt-stats ??  labuser@re0> show host-path ddos all-policers This issue affects Junos OS Evolved:  * All versions before 21.4R3-S8-EVO,  * from 22.2 before 22.2R3-S4-EVO,  * from 22.3 before 22.3R3-S4-EVO,  * from 22.4 before 22.4R3-S3-EVO,  * from 23.2 before 23.2R2-EVO,  * from 23.4 before 23.4R1-S1-EVO, 23.4R2-EVO,  * from 24.2 before 24.2R2-EVO.