An Improper Validation of Integrity Check Value and Improper Enforcement of Message Integrity During Transmission in a Communication Channel vulnerability in subscriber services of Juniper Networks Junos OS and Junos OS Evolved allows an on-path attacker between a RADIUS server and the RADIUS client to bypass authentication.

The RADIUS Protocol under RFC 2865 is susceptible to forgery attacks by a local attacker who can modify any valid Response (Access-Accept, Access-Reject, or Access-Challenge) to any other response using a chosen-prefix collision attack against MD5 Response Authenticator signature. 

This issue affects:

Junos OS: 

• all versions before 21.4R3-S11, 
• from 22.2 before 22.2R3-S7, 
• from 22.4 before 22.4R3-S7, 
• from 23.2 before 23.2R2-S4, 
• from 23.4 before 23.4R2-S5, 
• from 24.2 before 24.2R2-S1, 
• from 24.4 before 24.4R1-S3, 24.4R2.

Junos OS Evolved:

• from 23.4-EVO before 23.4R2-S5-EVO,
• from 24.2-EVO before 24.2R2-S1-EVO,
• from 24.4-EVO before 24.4R1-S3-EVO, 24.4R2-EVO.

Note: Subscriber Services for Junos OS Evolved were only introduced in 23.4R1-EVO and are only available on specific platforms.

Systems configured for RADIUS-based subscriber authentication are vulnerable to this issue:

[access radius-server]

[access profile <name> radius-server]

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

This issue was discovered during external security research.

A new configuration flag, called 'message-authenticator' within the radius-server configuration, which is disabled by default, enforces checking of the Message-Authenticator attribute in all Access-Response messages from a RADIUS server.

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

• Junos OS 21.4R3-S11, 22.2R3-S7, 22.4R3-S7, 23.2R2-S4, 23.4R2-S5, 24.2R2-S1, 24.4R1-S3, 24.4R2, 25.2R1, and all subsequent releases.
• Junos OS Evolved 23.4R2-S5-EVO, 24.2R2-S1-EVO, 24.4R1-S3-EVO, 24.4R2-EVO, 25.1R1-EVO, and all subsequent releases.

This issue is being tracked as 1822300 which is visible on the Customer Support website.

Note: Juniper SIRT's policy is not to evaluate releases which are beyond End of Engineering (EOE) or End of Life (EOL).

Enable RADIUS over TLS (RADSEC) to encrypting RADIUS traffic using TLS:

[access radsec destination <ID> address x.x.x.x]

2025-07-09: Initial Publication
2025-07-14: 'message-authenticator' configuration is DISABLED by default

• 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
• https://www.cve.org/CVERecord?id=CVE-2024-3596

This vulnerability was publicly disclosed by Sharon Goldberg, Miro Haller, Nadia Heninger, Mike Milano, Dan Shumow, Marc Stevens, and Adam Suhl.