An improper check for unusual or exceptional conditions in Juniper Networks Junos OS and Junos OS Evolved Routing Protocol Daemon (RPD) service allows an attacker to send a valid BGP FlowSpec message thereby causing an unexpected change in the route advertisements within the BGP FlowSpec domain leading to disruptions in network traffic causing a Denial of Service (DoS) condition. Continued receipt of these update messages will cause a sustained Denial of Service condition. This issue affects Juniper Networks: Junos OS: All versions prior to 17.3R3-S10 with the exceptions of 15.1X49-D240 on SRX Series and 15.1R7-S8 on EX Series.

17.3 versions prior to 17.3R3-S10.

17.4 versions prior to 17.4R2-S12, 17.4R3-S4.

18.1 versions prior to 18.1R3-S12.

18.2 versions prior to 18.2R2-S8, 18.2R3-S6.

18.3 versions prior to 18.3R3-S4.

18.4 versions prior to 18.4R1-S8, 18.4R2-S6, 18.4R3-S6.

19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S3.

19.2 versions prior to 19.2R3-S1.

19.3 versions prior to 19.3R2-S5, 19.3R3-S1.

19.4 versions prior to 19.4R1-S3, 19.4R2-S3, 19.4R3.

20.1 versions prior to 20.1R2.

20.2 versions prior to 20.2R1-S3 20.2R2.

20.3 versions prior to 20.3R1-S1, 20.3R2. Junos OS Evolved: All versions prior to 20.3R1-S1-EVO, 20.3R2-EVO.