Skip to content
Noroxi
NVD / CVE Program· CNA juniper

CVE-2026-21912: Junos OS: MX10k Series: 'show system firmware' CLI command may lead to LC480 or LC2101 line card reset

MediumCVSS 6.8 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.11% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Juniper Networks Junos OS 21.2R3-S10, 21.4R3-S9, 22.2R3-S7.

Low priority for now. Upgrade to Juniper Networks Junos OS 21.2R3-S10, 21.4R3-S9, 22.2R3-S7 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Jan 15, 2026
Updated
Jun 17, 2026
EPSS
0.1% · 1th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
27 / 40 · 6.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · juniper
5.5
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-21912

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits every 10 minutes on paid plans, on the hour on the free plan.

Your free account also gets you

  • CVE alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools, at most 30 a day (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for juniper records
Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
juniperjunos
juniperlc2101
juniperlc480
junipermx10004
junipermx10008

Versions reported by the vendor

Affected version ranges reported by the assigning authority (juniper). Independent of NVD's CPE analysis and usually ahead of it.

  • Juniper Networks Junos OS

    • before 21.2R3-S10affected · semver
    • 21.4 and later · before 21.4R3-S9affected · semver
    • 22.2 and later · before 22.2R3-S7affected · semver
    • 22.4 and later · before 22.4R3-S6affected · semver
    • 23.2 and later · before 23.2R2-S2affected · semver
    • 23.4 and later · before 23.4R2-S3affected · semver
    • 24.2 and later · before 24.2R2affected · semver
Affected versions · NVD (8)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • juniper junosbefore 21.2
  • juniper junos21.2
  • juniper junos21.4
  • juniper junos22.2
  • juniper junos22.4
  • juniper junos23.2
  • juniper junos23.4
  • juniper junos24.2

Same product

juniper: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-36845Junos OS: EX and SRX Series: A PHP vulnerability in J-Web allows an unauthenticated to control an important environment variableKEV
    98Now
  • CVE-2023-36846Junos OS: SRX Series: A vulnerability in J-Web allows an unauthenticated attacker to upload arbitrary filesKEV
    79This week
  • CVE-2023-36844Junos OS: EX Series: A PHP vulnerability in J-Web allows an unauthenticated attacker to control important environment variablesKEV
    78This week

Published before and after this one in the same product

  • ← EarlierCVE-2026-21909Jan 15, 2026 · Junos OS and Junos OS Evolved: Receipt of specific IS-IS update packet causes memory leak leading to RPD crash
    28Monitor
  • ← EarlierCVE-2026-21910Jan 15, 2026 · Junos OS: EX4k Series, QFX5k Series: In an EVPN-VXLAN configuration link flaps cause Inter-VNI traffic drop
    28Monitor
  • Later →CVE-2026-21913Jan 15, 2026 · Junos OS: EX4000: A high volume of traffic destined to the device leads to a crash and restart
    34Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Juniper Networks Junos OS21.2R3-S10Vendor (CNA)
Juniper Networks Junos OS21.4R3-S9Vendor (CNA)
Juniper Networks Junos OS22.2R3-S7Vendor (CNA)
Juniper Networks Junos OS22.4R3-S6Vendor (CNA)
Juniper Networks Junos OS23.2R2-S2Vendor (CNA)
Juniper Networks Junos OS23.4R2-S3Vendor (CNA)
Juniper Networks Junos OS24.2R2Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2024-47494461 days apartJunos OS: Due to a race condition AgentD process causes a memory corruption and FPC reset
    32Monitor

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
X

Weakness class (CWE)

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

CVSS 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/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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records