A Use After Free vulnerability was identified in the 802.1X authentication daemon (dot1xd) of Juniper Networks Junos OS and Junos OS Evolved that could allow an authenticated, network-adjacent attacker flapping a port to crash the dot1xd process, leading to a Denial of Service (DoS), or potentially execute arbitrary code within the context of the process running as root.

The issue is specific to the processing of a change in authorization (CoA) when a port bounce occurs. A pointer is freed but was then referenced later in the same code path. Successful exploitation is outside the attacker's direct control due to the specific timing of the two events required to execute the vulnerable code path.

This issue affects systems with 802.1X authentication port-based network access control (PNAC) enabled.

This issue affects:

Junos OS: 

• from 23.2R2-S1 before 23.2R2-S5, 
• from 23.4R2 before 23.4R2-S6, 
• from 24.2 before 24.2R2-S3, 
• from 24.4 before 24.4R2-S1, 
• from 25.2 before 25.2R1-S2, 25.2R2; 

Junos OS Evolved: 

• from 23.2R2-S1 before 23.2R2-S5-EVO, 
• from 23.4R2 before 23.4R2-S6-EVO, 
• from 24.2 before 24.2R2-S3-EVO, 
• from 24.4 before 24.4R2-S1-EVO, 
• from 25.2 before 25.2R1-S2-EVO, 25.2R2-EVO.

This issue requires support for 802.1X be enabled. For example:

[protocols dot1x authenticator ...]

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

This issue was found during internal product security testing or research.

The following software releases have been updated to resolve this specific issue:
Junos OS 23.2R2-S5, 23.4R2-S6, 24.2R2-S3, 24.4R2-S1, 25.2R1-S2, 25.2R2, 25.4R1, and all subsequent releases.
Junos OS Evolved: 23.2R2-S5-EVO, 23.4R2-S6-EVO, 24.2R2-S3-EVO, 24.4R2-S1-EVO, 25.2R1-S2-EVO, 25.2R2-EVO, 25.4R1-EVO,

This issue is being tracked as 1896371 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).

There are no known workarounds for this issue.

2026-01-14: 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 Security Vulnerability - How to Contact the Juniper Networks Security Incident Response Team