A Denial of Service (DoS) vulnerability in the processing of a flood of specific ARP traffic in Juniper Networks Junos OS on the EX4300 switch, sent from the local broadcast domain, may allow an unauthenticated network-adjacent attacker to trigger a PFEMAN watchdog timeout, causing the Packet Forwarding Engine (PFE) to crash and restart. After the restart, transit traffic will be temporarily interrupted until the PFE is reprogrammed. In a virtual chassis (VC), the impacted Flexible PIC Concentrator (FPC) may split from the VC temporarily, and join back into the VC once the PFE restarts. Continued receipt and processing of these packets will create a sustained Denial of Service (DoS) condition. This issue affects Juniper Networks Junos OS on the EX4300: All versions prior to 15.1R7-S12; 18.4 versions prior to 18.4R2-S10, 18.4R3-S11; 19.1 versions prior to 19.1R3-S8; 19.2 versions prior to 19.2R1-S9, 19.2R3-S4; 19.3 versions prior to 19.3R3-S5; 19.4 versions prior to 19.4R2-S6, 19.4R3-S7; 20.1 versions prior to 20.1R3-S3; 20.2 versions prior to 20.2R3-S3; 20.3 versions prior to 20.3R3-S2; 20.4 versions prior to 20.4R3-S1; 21.1 versions prior to 21.1R3; 21.2 versions prior to 21.2R2-S1, 21.2R3; 21.3 versions prior to 21.3R1-S2, 21.3R2.