An Incomplete List of Disallowed Inputs vulnerability in Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on QFX5000 Series and EX4600 Series allows an adjacent unauthenticated attacker which sends a high rate of specific multicast traffic to cause control traffic received from the network to be dropped. This will impact control protocols (including but not limited to routing-protocols) and lead to a Denial of Service (DoS).

Continued receipt of this specific multicast traffic will create a sustained Denial of Service (DoS) condition.

This issue affects Juniper Networks Junos OS on QFX5000 and EX4600 Series:

• All versions prior to 17.3R3-S12;
• 17.4 versions prior to 17.4R3-S5;
• 18.3 versions prior to 18.3R3-S5;
• 18.4 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-S3;
• 20.1 versions prior to 20.1R2-S2, 20.1R3-S1;
• 20.2 versions prior to 20.2R3-S2;
• 20.3 versions prior to 20.3R3;
• 20.4 versions prior to 20.4R2-S2, 20.4R3;
• 21.1 versions prior to 21.1R1-S1, 21.1R2.

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-2021-31370 .

The following software releases have been updated to resolve this specific issue: 17.3R3-S12, 17.4R3-S5, 18.3R3-S5, 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S3, 19.4R1-S4, 19.4R3-S3, 20.1R2-S2, 20.1R3-S1, 20.2R3-S2, 20.3R3, 20.4R2-S2, 20.4R3, 21.1R1-S1, 21.1R2, 21.2R1, and all subsequent releases.

This issue is being tracked as  1576488 .

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

Please ensure you have a loopback filter applied to drop unneeded multicast traffic.

You can find further information on such filters in https://www.rfc-editor.org/rfc/rfc6192 and in "Hardening Junos Devices, 2nd Edition" at https://www.juniper.net/documentation/jnbooks/us/en/day-one-books

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-2021-31370: Junos OS: QFX5000 Series and EX4600 Series: Control traffic might be dropped if a high rate of specific multicast traffic is received