CVE-2026-21912

Junos OS: MX10k Series: 'show system firmware' CLI command may lead to LC480 or LC2101 line card reset

MEDIUM

4.7

CVSS Score

Published: January 15, 2026 at 08:24 PM UTC

Updated: June 17, 2026 at 10:19 AM UTC

1 product affected across 1 vendorJunos

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Severity

MEDIUM4.7

Exploit prediction

EPSS 0.1%

SSVC

No known exploit

Description

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Junos · Juniper Networks

95%

v < 21.2v < 21.2R3-S1021.4 ≤ v < 21.4R3-S922.2 ≤ v < 22.2R3-S722.4 ≤ v < 22.4R3-S623.2 ≤ v < 23.2R2-S223.4 ≤ v < 23.4R2-S324.2 ≤ v < 24.2R221.2 21.2 r1 21.2 r1-s1 21.2 r1-s2 21.2 r2 21.2 r2-s1 21.2 r2-s2 21.2 r3 21.2 r3-s1 21.2 r3-s2 21.2 r3-s3 21.2 r3-s4 21.2 r3-s5 21.2 r3-s6 21.2 r3-s7 21.2 r3-s8 21.2 r3-s9 21.4 21.4 r1 21.4 r1-s1 21.4 r1-s2 21.4 r2 21.4 r2-s1 21.4 r2-s2 21.4 r3 21.4 r3-s1 21.4 r3-s2 21.4 r3-s3 21.4 r3-s4 21.4 r3-s5 21.4 r3-s6 21.4 r3-s7 21.4 r3-s8 22.2 22.2 r1 22.2 r1-s1 22.2 r1-s2 22.2 r2 22.2 r2-s1 22.2 r2-s2 22.2 r3 22.2 r3-s1 22.2 r3-s2 22.2 r3-s3 22.2 r3-s4 22.2 r3-s5 22.2 r3-s6 22.4 22.4 r1 22.4 r1-s1 22.4 r1-s2 22.4 r2 22.4 r2-s1 22.4 r2-s2 22.4 r3 22.4 r3-s1 22.4 r3-s2 22.4 r3-s3 22.4 r3-s4 22.4 r3-s5 23.2 23.2 r1 23.2 r1-s1 23.2 r1-s2 23.2 r2 23.2 r2-s1 23.4 23.4 r1 23.4 r1-s1 23.4 r1-s2 23.4 r2 23.4 r2-s1 23.4 r2-s2 24.2 24.2 r1 24.2 r1-s1 24.2 r1-s2

Affected range stops below 21.2R3-S10, so it looks safe — our inference, not a vendor statement

Affected range stops below 21.4R3-S9, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.2R3-S7, so it looks safe — our inference, not a vendor statement

Affected range stops below 22.4R3-S6, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.2R2-S2, so it looks safe — our inference, not a vendor statement

Affected range stops below 23.4R2-S3, so it looks safe — our inference, not a vendor statement

Affected range stops below 24.2R2, so it looks safe — our inference, not a vendor statement

juniper-lc2101 (environment) · juniper-lc480 (environment) · juniper-mx10004 (environment) · juniper-mx10008 (environment)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (2)

Vendor Advisory

Source: cverecord

https://supportportal.juniper.net/JSA106011

Vendor Advisory

Source: cverecord

https://kb.juniper.net/JSA106011

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.7MEDIUM[email protected]

Attack Vector: LOCAL
Complexity: HIGH
Privileges: LOW
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusANALYZED

CWE

CWE-367

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