CVE-2026-21912 is a Time-of-check Time-of-use (TOCTOU) race condition in Juniper Networks Junos OS on MX10k Series, specifically affecting LC480 and LC2101 line cards. A local, low-privileged attacker can repeatedly execute the 'show system firmware' CLI command to cause a line card to crash and restart, potentially leading to a chassisd crash and core dump. Rated Medium (CVSS 5.5), this vulnerability has a local attack vector, low attack complexity, and high impact on availability. There is no evidence of active exploitation, public exploit code, or Metasploit/Nuclei modules, though it has garnered some community discussion.
| Vendor | Product | Version(s) | CPE |
|---|---|---|---|
>= 0, < 21.2R3-S10CPE match | cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:* | ||
>= 21.4, < 21.4R3-S9CPE match | cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:* | ||
>= 22.2, < 22.2R3-S7CPE match | cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:* | ||
>= 22.4, < 22.4R3-S6CPE match | cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:* | ||
>= 23.2, < 23.2R2-S2CPE match | cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:* |
CVSS version used by this source: 4.0
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:X/RE:M/U:Amber
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