What is CVE-2026-21912?

CVE-2026-21912 is a medium-severity vulnerability in Juniper Junos, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 5.5/10. Published 2026-01-15.

How severe is CVE-2026-21912?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Vulnerability in Juniper Junos

CVE-2026-21912

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 fir…

Vulnerability class: TOCTOU (Time-of-Check to Time-of-Use)

EPSS: 0.001 (1.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

Affected products

Juniper Junos — versions 21.2, 21.4, 22.2
Juniper Lc2101
Juniper Lc480
Juniper Mx10004
Juniper Mx10008
Juniper Networks Junos Os — versions 0, 21.4, 22.2

Weakness classification (CWE)

CWE-367 — Time-of-check Time-of-use (TOCTOU) Race Condition

References

sirt@juniper.net (vendor-advisory, Vendor Advisory)
sirt@juniper.net (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-21912?: CVE-2026-21912 is a medium-severity vulnerability in Juniper Junos, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 5.5/10. Published 2026-01-15.
How severe is CVE-2026-21912?: Medium severity. CVSS v3 base score is 5.5 out of 10.