Product:
Junos OS
Summary
A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability exists in the method to collect FPC Ethernet firmware statistics on MX10k Series. A local, low-privileged attacker can execute the ‘show system firmware’ CLI command to cause an LC480 or LC2101 line card to reset. Repeated execution of this command can lead to the line card crashing and restarting, and may also cause the chassisd to crash and generate a core dump.
Details
| Severity | Base Score | CVE |
|---|---|---|
| MEDIUM | 6.8 | CVE-2026-21912 |
Exploitation
To exploit this vulnerability, an attacker with low privileges can repeatedly execute the ‘show system firmware’ command on affected MX10k Series systems. This action can trigger a race condition that results in the line card crashing and restarting, potentially leading to further system instability.
Affected Products
- Junos OS on MX10k Series: all versions before 21.2R3-S10
- Junos OS on MX10k Series: from 21.4 before 21.4R3-S9
- Junos OS on MX10k Series: from 22.2 before 22.2R3-S7
- Junos OS on MX10k Series: from 22.4 before 22.4R3-S6
- Junos OS on MX10k Series: from 23.2 before 23.2R2-S2
- Junos OS on MX10k Series: from 23.4 before 23.4R2-S3
- Junos OS on MX10k Series: from 24.2 before 24.2R2
Mitigation
To mitigate this vulnerability, it is recommended to upgrade to the latest versions of Junos OS that are not affected by this issue. Regularly applying security updates and patches can help protect against potential exploitation.