A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in the method to collect FPC Ethernet firmware statistics of Juniper Networks Junos OS on MX10k Series allows a local, low-privileged attacker executing the 'show system firmware' CLI command to cause an LC480 or LC2101 line card to reset.

On MX10k Series systems with LC480 or LC2101 line cards, repeated execution of the 'show system firmware' CLI command can cause the line card to crash and restart. Additionally, some time after the line card crashes, chassisd may also crash and restart, generating a core dump.

This issue affects Junos OS on the MX10k Series: 

• all versions before 21.2R3-S10, 
• from 21.4 before 21.4R3-S9, 
• from 22.2 before 22.2R3-S7, 
• from 22.4 before 22.4R3-S6, 
• from 23.2 before 23.2R2-S2, 
• from 23.4 before 23.4R2-S3, 
• from 24.2 before 24.2R2.

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

This issue was seen during production usage.

The following software releases have been updated to resolve this specific issue: Junos OS 21.2R3-S10, 21.4R3-S9, 22.2R3-S7, 22.4R3-S6, 23.2R2-S2, 23.4R2-S3, 24.2R2, 24.4R1, and all subsequent releases.

This issue is being tracked as 1695340 and 1696186 which are 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).

Use CLI authorization to limit access to the 'show system firmware' command.

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