A vulnerability in the NETISR network queue functionality of Juniper Networks Junos OS kernel allows an attacker to cause a Denial of Service (DoS) by sending crafted genuine packets to a device. During an attack, the routing protocol daemon (rpd) CPU may reach 100% utilization, yet FPC CPUs forwarding traffic will operate normally. This attack occurs when the attackers' packets are sent over an IPv4 unicast routing equal-cost multi-path (ECMP) unilist selection. Continued receipt and processing of these packets will create a sustained Denial of Service (DoS) condition. An indicator of compromise may be to monitor NETISR drops in the network with the assistance of JTAC. Please contact JTAC for technical support for further guidance. This issue affects: Juniper Networks Junos OS 17.3 version 17.3R3-S9 and later versions prior to 17.3R3-S12; 17.4 version 17.4R3-S3 and later versions prior to 17.4R3-S5; 18.1 version 18.1R3-S11 and later versions prior to 18.1R3-S13; 18.2 version 18.2R3-S6 and later versions; 18.3 version 18.3R3-S4 and later versions prior to 18.3R3-S5; 18.4 version 18.4R3-S5 and later versions prior to 18.4R3-S9; 19.1 version 19.1R3-S3 and later versions prior to 19.1R3-S7. This issue does not affect Juniper Networks Junos OS versions prior to 17.3R3-S9. This issue does not affect Juniper Networks Junos OS Evolved.