Instituto Nacional de ciberseguridad. Sección Incibe
Instituto Nacional de Ciberseguridad. Sección INCIBE-CERT

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CVE-2026-21912

Severity CVSS v4.0:
MEDIUM
Type:
Unavailable / Other
Publication date:
15/01/2026
Last modified:
25/02/2026

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 &amp;#39;show system firmware&amp;#39; CLI command to cause an LC480 or LC2101 line card to reset.<br /> <br /> On MX10k Series systems with LC480 or LC2101 line cards, repeated execution of the &amp;#39;show system firmware&amp;#39; 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: <br /> <br /> <br /> <br /> * all versions before 21.2R3-S10, <br /> * from 21.4 before 21.4R3-S9, <br /> * from 22.2 before 22.2R3-S7, <br /> * from 22.4 before 22.4R3-S6, <br /> * from 23.2 before 23.2R2-S2, <br /> * from 23.4 before 23.4R2-S3, <br /> * from 24.2 before 24.2R2.

Impact

Vector 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/AU:Y/R:A/RE:M/U:Amber CVSS v4.0 Severity and Metrics:

Base Score: 6.80 MEDIUM
Vector: 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/AU:Y/R:A/RE:M/U:Amber

Attack Vector (AV): Local
Attack Complexity (AC): Low
Attack Requirements (AT): None
Privileges Required (PR): Low
User Interaction (UI): None
Confidentiality (VC): None
Integrity (VI): None
Availability (VA): High
Confidentiality (SC): None
Integrity (SI): None
Availability (SA): Low
Automatable (AU): Yes
Recovery (R): Automatic
Vulnerability Response Effort (RE): Moderate
Provider Urgency (U): Amber

Base Score 4.0
6.80
Severity 4.0
MEDIUM
Vector 3.x
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS v3.1 Severity and Metrics:

Base Score: 5.50 MEDIUM
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector (AV): Local
Attack Complexity (AC): Low
Privileges Required (PR): Low
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): None
Integrity (I): None
Availability (A): High

Base Score 3.x
5.50
Severity 3.x
MEDIUM

Vulnerable products and versions

CPE From Up to
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:* 21.2 (excluding)
cpe:2.3:o:juniper:junos:21.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s3:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s4:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s5:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:21.2:r3-s6:*:*:*:*:*:*

To consult the complete list of CPE names with products and versions, see this page


References to Advisories, Solutions, and Tools