A buffer overflow vulnerability in the TCP/IP stack of Juniper Networks Junos OS allows an attacker to send specific sequences of packets to the device thereby causing a Denial of Service (DoS). By repeatedly sending these sequences of packets to the device, an attacker can sustain the Denial of Service (DoS) condition. The device will abnormally shut down as a result of these sent packets. A potential indicator of compromise will be the following message in the log files: "eventd[13955]: SYSTEM_ABNORMAL_SHUTDOWN: System abnormally shut down" This issue is only triggered by traffic destined to the device. Transit traffic will not trigger this issue. This issue affects: Juniper Networks Junos OS 12.3 versions prior to 12.3R12-S19; 15.1 versions prior to 15.1R7-S10; 17.3 versions prior to 17.3R3-S12; 18.4 versions prior to 18.4R2-S9, 18.4R3-S9; 19.1 versions prior to 19.1R3-S7; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S7, 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3-S1; 20.4 versions prior to 20.4R2-S2, 20.4R3; 21.1 versions prior to 21.1R2; 21.2 versions prior to 21.2R1-S1, 21.2R2.