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FirefoxWeb browser · Mozilla

CVE-2025-14329

HIGH · 8.8 CVSS v3.1 Published 2025-12-09
Fix available
A fix is available. Upgrade to 140.6.0 / 146.0 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

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
Privilege escalation in the Netmonitor component. This vulnerability was fixed in Firefox 146, Firefox ESR 140.6, Thunderbird 146, and Thunderbird 140.6.

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

A privilege escalation vulnerability exists in the Netmonitor component of Firefox and Thunderbird. The Netmonitor is the developer tools panel used for inspecting network requests. This flaw allows a malicious web page or content to potentially elevate privileges through the network monitoring functionality, possibly by bypassing same-origin restrictions or executing privileged operations from within the Netmonitor context.

MitigationUpgrade affected installations to Firefox 146, Firefox ESR 140.6, Thunderbird 146, or Thunderbird 140.6 or later. Apply standard enterprise patch management procedures to ensure all browser installations are updated.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FirefoxWeb browser
Affected:< 140.6.0< 146.0
ThunderbirdApplication
Affected:< 140.6.0< 146.0

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
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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 installed Mozilla product
    Open the application and check if it is Firefox or Thunderbird by looking at the window title or application name in the system
    Affected if The product is Firefox or Thunderbird
  2. Check Firefox version
    In Firefox, type about:firefox in the address bar or go to Menu > Help > About Firefox to see the version number
    Affected if The installed version is below 140.6.0 or below 146.0 (check both ranges)
  3. Check Thunderbird version
    In Thunderbird, type about:thunderbird in the address bar or go to Menu > Help > About Thunderbird to see the version number
    Affected if The installed version is below 140.6.0 or below 146.0 (check both ranges)
  4. Verify Developer Tools accessibility
    In Firefox, try opening Developer Tools (F12 or Ctrl+Shift+I) and confirm the Network monitor tab is accessible. In enterprise environments, this may be disabled via group policy or the dom.webdeveloper.enabled preference in about:config
    Affected if The Netmonitor component is accessible and the version is in the affected range

A user is affected if they have Firefox or Thunderbird installed with a version below 140.6.0 or below 146.0 AND have access to the Netmonitor component in Developer Tools.

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.

dbcve · scoped
Upgrade available Upgrade to 140.6.0 / 146.0 or later
Fixed in 140.6.0146.0
Interim mitigation

Upgrade affected installations to Firefox 146, Firefox ESR 140.6, Thunderbird 146, or Thunderbird 140.6 or later. Apply standard enterprise patch management procedures to ensure all browser installations are updated.

Recommended fix High confidence

Firefox 146, Firefox ESR 140.6, Thunderbird 146, or Thunderbird 140.6

  1. Check current Firefox version: Open Firefox, click Help > About Firefox
  2. Check current Thunderbird version: Open Thunderbird, click Help > About Thunderbird
  3. Download Firefox 146 (or Firefox ESR 140.6 for extended support) from mozilla.org
  4. Download Thunderbird 146 (or Thunderbird 140.6) from mozilla.org
  5. Install the downloaded update by running the installer and following prompts
  6. Restart the browser/mail client after the update completes

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.

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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-2025-14329 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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data