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;
• 17.4 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.

The following minimal configuration is required to potentially hit this issue:

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was seen during production usage.

This issue has been assigned  CVE-2021-0211 .

The following software releases have been updated to resolve this specific issue:

Junos OS: 15.1R7-S8, 15.1X49-D240, 17.3R3-S10, 17.4R2-S12, 17.4R3-S4, 18.1R3-S12, 18.2R2-S8, 18.2R3-S6, 18.3R3-S4, 18.4R1-S8, 18.4R2-S6, 18.4R3-S6, 19.1R2-S2, 19.1R3-S3, 19.2R3-S1, 19.3R2-S5, 19.3R3-S1, 19.4R1-S3, 19.4R2-S3, 19.4R3, 20.1R2, 20.2R1-S3, 20.2R2, 20.3R1-S1, 20.3R2, 20.4R1, and all subsequent releases.

Junos OS Evolved: 20.3R1-S1-EVO, 20.3R2-EVO, 20.4R1-EVO, and all subsequent releases.

This issue is being tracked as  1539109 .

Software releases or updates are available for download at https://www.juniper.net/support/downloads/ .

There are no viable workarounds for this issue.

• KB16613: Overview of the Juniper Networks SIRT Quarterly Security Bulletin Publication Process [juniper.net]
• KB16765: In which releases are vulnerabilities fixed? [juniper.net]
• KB16446: Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories [juniper.net]
• Report a Security Vulnerability - How to Contact the Juniper Networks Security Incident Response Team
• CVE-2021-0211 at cve.mitre.org