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OS Command InjectionWeakness · CWE-78

CVE-2025-43979

HIGH · 7.4 CVSS v3.1 Published 2025-08-05
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
83/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An issue was discovered on FIRSTNUM JC21A-04 devices through 2.01ME/FN that allows authenticated attackers to execute arbitrary OS system commands with root privileges via crafted payloads to the xml_action.cgi?method= endpoint.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Authenticated command injection vulnerability in FIRSTNUM JC21A-04 devices (firmware 2.01ME/FN and earlier). The xml_action.cgi endpoint accepts user-supplied input via the method parameter without proper sanitization, allowing authenticated attackers to inject and execute arbitrary OS commands with root privileges.

MitigationRestrict network access to the device management interface; contact vendor for firmware patch; if patch unavailable, implement network segmentation and monitor for exploitation attempts.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the device model
    Locate the device label, web interface, or SNMP inventory to confirm the model is FIRSTNUM JC21A-04
    Affected if The device model is JC21A-04 from FIRSTNUM
  2. Determine the installed firmware version
    Access the device web interface administrative panel or check system information page for the firmware version string (look for versions like 2.01ME/FN or earlier)
    Affected if The firmware version is 2.01ME/FN or any version prior to 2.01ME/FN
  3. Verify xml_action.cgi is exposed
    Attempt to access the URI /cgi-bin/xml_action.cgi on the device management interface (port 80/443 or custom management port)
    Affected if The endpoint responds and accepts parameters
  4. Confirm authentication is in use or accessible
    Check whether the device administrative interface requires authentication, and verify whether valid credentials can be obtained (default credentials documentation, password policy, or authentication mechanism status)
    Affected if Authentication is enabled and valid credentials exist or can be obtained, making the command injection reachable

You are affected if the device is a FIRSTNUM JC21A-04 running firmware 2.01ME/FN or earlier, and the xml_action.cgi endpoint is accessible with valid administrative credentials.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Restrict network access to the device management interface; contact vendor for firmware patch; if patch unavailable, implement network segmentation and monitor for exploitation attempts.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-43979 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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