CVE-2026-21912

Summary

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 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.

Affected Software

VendorProductVersion RangeStatus
Juniper NetworksJunos OS0 < 21.2R3-S10affected
Juniper NetworksJunos OS21.4 < 21.4R3-S9affected
Juniper NetworksJunos OS22.2 < 22.2R3-S7affected
Juniper NetworksJunos OS22.4 < 22.4R3-S6affected
Juniper NetworksJunos OS23.2 < 23.2R2-S2affected
Juniper NetworksJunos OS23.4 < 23.4R2-S3affected
Juniper NetworksJunos OS24.2 < 24.2R2affected

Weaknesses

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

Workarounds

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

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References