An Improper Check for Unusual or Exceptional Conditions vulnerability combined with Improper Handling of Exceptional Conditions in Juniper Networks Junos OS on QFX Series and PTX Series allows an unauthenticated network based attacker to cause increased FPC CPU utilization by sending specific IP packets which are being VXLAN encapsulated leading to a partial Denial of Service (DoS).

Continued receipted of these specific traffic will create a sustained Denial of Service (DoS) condition.

This issue affects:
Juniper Networks Junos OS on QFX Series:

• All versions prior to 17.3R3-S11;
• 17.4 versions prior to 17.4R2-S13, 17.4R3-S4;
• 18.1 versions prior to 18.1R3-S12;
• 18.2 versions prior to 18.2R2-S8, 18.2R3-S7;
• 18.3 versions prior to 18.3R3-S4;
• 18.4 versions prior to 18.4R1-S8, 18.4R2-S7, 18.4R3-S7;
• 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S4;
• 19.2 versions prior to 19.2R1-S6, 19.2R3-S2;
• 19.3 versions prior to 19.3R3-S1;
• 19.4 versions prior to 19.4R2-S3, 19.4R3-S1;
• 20.1 versions prior to 20.1R2, 20.1R3;
• 20.2 versions prior to 20.2R2, 20.2R3;
• 20.3 versions prior to 20.3R1-S1, 20.3R2.

Juniper Networks Junos OS on PTX Series:

• All versions prior to 18.4R3-S9;
• 19.1 versions prior to 19.1R3-S6;
• 19.2 versions prior to 19.2R1-S7, 19.2R3-S3;
• 19.3 versions prior to 19.3R2-S6, 19.3R3-S3;
• 19.4 versions prior to 19.4R1-S4, 19.4R3-S5;
• 20.1 versions prior to 20.1R2-S2, 20.1R3;
• 20.2 versions prior to 20.2R3-S1;
• 20.3 versions prior to 20.3R2-S1, 20.3R3;
• 20.4 versions prior to 20.4R2-S1, 20.4R3;
• 21.1 versions prior to 21.1R1-S1, 21.1R2.

An minimal example VXLAN configuration affected would be:

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-2021-31361 .

The following software releases have been updated to resolve this specific issue for QFX Series: 17.3R3-S11, 17.4R2-S13, 17.4R3-S4, 18.1R3-S12, 18.2R2-S8, 18.2R3-S7, 18.3R3-S4, 18.4R1-S8, 18.4R2-S7, 18.4R3-S7, 19.1R1-S6, 19.1R2-S2, 19.1R3-S4, 19.2R1-S6, 19.2R3-S2, 19.3R3-S1, 19.4R2-S3, 19.4R3-S1, 20.1R2, 20.1R3, 20.2R2, 20.2R3, 20.3R1-S1, 20.3R2, 20.4R1, and all subsequent releases.

The following software releases have been updated to resolve this specific issue for PTX Series: 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S3, 19.4R1-S4, 19.4R3-S5, 20.1R2-S2, 20.1R3, 20.2R3-S1, 20.3R2-S1, 20.3R3, 20.4R2-S1, 20.4R3, 21.1R1-S1, 21.1R2, 21.2R1, and all subsequent releases.

This issue is being tracked as  1490063  and  1584197 .

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

2021-10-13: Initial Publication.

• 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 Vulnerability - How to Contact the Juniper Networks Security Incident Response Team
• CVE-2021-31361: Junos OS: QFX Series and PTX Series: FPC resource usage increases when certain packets are processed which are being VXLAN encapsulated