In broadband environments, including but not limited to Enhanced Subscriber Management, (CHAP, PPP, DHCP, etc.), on Juniper Networks Junos OS devices where RADIUS servers are configured for managing subscriber access and a subscriber is logged in and then requests to logout, the subscriber may be forced into a "Terminating" state by an attacker who is able to send spoofed messages appearing to originate from trusted RADIUS server(s) destined to the device in response to the subscriber's request. These spoofed messages cause the Junos OS General Authentication Service (authd) daemon to force the broadband subscriber into this "Terminating" state which the subscriber will not recover from thereby causing a Denial of Service (DoS) to the endpoint device. Once in the "Terminating" state, the endpoint subscriber will no longer be able to access the network. Restarting the authd daemon on the Junos OS device will temporarily clear the subscribers out of the "Terminating" state. As long as the attacker continues to send these spoofed packets and subscribers request to be logged out, the subscribers will be returned to the "Terminating" state thereby creating a persistent Denial of Service to the subscriber.

An indicator of compromise may be seen by displaying the output of "show subscribers summary". The presence of subscribers in the "Terminating" state may indicate the issue is occurring.

This issue affects:

Juniper Networks Junos OS

• 17.3 versions prior to 17.3R3-S12;
• 17.4 versions prior to 17.4R3-S5;
• 18.1 versions prior to 18.1R3-S13;
• 18.2 versions prior to 18.2R3-S8;
• 18.3 versions prior to 18.3R3-S5;
• 18.4 versions prior to 18.4R2-S8, 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, 19.4R1-S4, 19.4R3-S3;
• 20.1 versions prior to 20.1R3;
• 20.2 versions prior to 20.2R3-S1;
• 20.3 versions prior to 20.3R3;
• 20.4 versions prior to 20.4R3;
• 21.1 versions prior to 21.1R2.

This issue does not affect:

Juniper Networks Junos OS

• 12.3 version 12.3R1 and later versions;
• 15.1 version 15.1R1 and later versions.

The following minimum system configuration is necessary to be potentially exposed to this issue:

* In broadband environments

* In Enhanced Subscriber Management environment (i.e., "system services subscriber-management enable" is configured)

* RADIUS server is configured for subscriber access (i.e., define RADIUS server at "access radius-server" or "access profile <> radius-server" hierarchy level)

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-2021-31378 .

The following software releases have been updated to resolve this specific issue: 17.3R3-S12, 17.4R3-S5, 18.1R3-S13, 18.2R3-S8, 18.3R3-S5, 18.4R2-S8, 18.4R3-S9, 19.1R3-S6, 19.2R1-S7, 19.2R3-S3, 19.3R2-S6, 19.3R3-S3, 19.4R1-S4, 19.4R3-S3, 20.1R3, 20.2R3-S1, 20.3R3, 20.4R3, 21.1R2, 21.2R1, and all subsequent releases.

This issue is being tracked as  1583090 .

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-2021-31378 at cve.mitre.org
• Tracing General Authentication Service (authd) Events for Troubleshooting