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FirefoxWeb browser · Mozilla

CVE-2025-14333

HIGH · 8.1 CVSS v3.1 Published 2025-12-09
Fix available
A fix is available. Upgrade to 140.6.0 / 146.0 or later.
See remediation →
90/100
Remediation priority · Urgent
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
Memory safety bugs present in Firefox ESR 140.5, Thunderbird ESR 140.5, Firefox 145 and Thunderbird 145. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. 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 · moderate confidence

Memory safety bugs in Firefox ESR 140.5, Thunderbird ESR 140.5, Firefox 145, and Thunderbird 145 caused memory corruption that could potentially be exploited for arbitrary code execution. This is a classic memory corruption vulnerability in the browser's rendering engine or JavaScript engine.

MitigationUpdate to Firefox 146, Firefox ESR 140.6, Thunderbird 146, or Thunderbird 140.6 to remediate the vulnerability. Deploy via enterprise patch management tools.

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

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/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 products
    Run 'firefox --version' and 'thunderbird --version' in terminal, or check the application via Help > About in the GUI
    Affected if Either Firefox or Thunderbird is present on the system
  2. Check Firefox version number
    Open Firefox and navigate to Help > About Firefox, or run 'firefox --version' from command line. Record the full version number (e.g., 140.5, 145.3, 146.0)
    Affected if Version is less than 140.6.0 OR between 141.0 and 145.x inclusive
  3. Check Thunderbird version number
    Open Thunderbird and navigate to Help > About Thunderbird, or run 'thunderbird --version' from command line. Record the full version number
    Affected if Version is less than 140.6.0 OR between 141.0 and 145.x inclusive
  4. Confirm version is in affected range
    Compare your recorded version against the affected ranges: < 140.6.0 or >= 141.0 but < 146.0
    Affected if The installed version falls within any of these vulnerable ranges

A user is affected if Firefox or Thunderbird is installed with a version lower than 140.6.0, or with a version from 141.x through 145.x.

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

Update to Firefox 146, Firefox ESR 140.6, Thunderbird 146, or Thunderbird 140.6 to remediate the vulnerability. Deploy via enterprise patch management tools.

Recommended fix High confidence

Firefox 146 (stable) or Firefox ESR 140.6 (ESR); Thunderbird 146 (stable) or Thunderbird 140.6 (ESR)

  1. Identify your current Firefox or Thunderbird version via Help > About
  2. If using Firefox 145, upgrade to Firefox 146
  3. If using Firefox ESR 140.5, upgrade to Firefox ESR 140.6
  4. If using Thunderbird 145, upgrade to Thunderbird 146
  5. If using Thunderbird ESR 140.5, upgrade to Thunderbird ESR 140.6
  6. Download the appropriate fixed version from www.mozilla.org
  7. Close the application completely before installing
  8. Install the update and restart the application
Caveat No breaking changes expected; this is a memory safety bugfix release

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

Scan for this in your stack

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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-2025-14333 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