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FirefoxWeb browser · Mozilla

CVE-2025-14330

CRITICAL · 9.8 CVSS v3.1 Published 2025-12-09
Fix available
A fix is available. Upgrade to 140.6.0 / 146.0 or later.
See remediation →
100/100
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
JIT miscompilation in the JavaScript Engine: JIT 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 · moderate confidence

JIT miscompilation vulnerability in Firefox's SpiderMonkey JavaScript engine. The Just-In-Time compiler produces incorrect machine code, which can lead to memory corruption and potentially allow arbitrary code execution when processing malicious JavaScript.

MitigationUpdate Firefox to version 146 or later, Firefox ESR to 140.6 or later, Thunderbird to 146 or later, or Thunderbird ESR to 140.6 or later. Apply via standard software update mechanisms.

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
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/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 Firefox or Thunderbird version
    Open Firefox or Thunderbird, click Help > About [Product Name], or navigate to about:support in the URL bar to view the version number
    Affected if The version displayed is below 140.6.0 or below 146.0
  2. Confirm product is in affected family
    Verify you are running Mozilla Firefox or Mozilla Thunderbird (not another browser or product that uses SpiderMonkey)
    Affected if The product is Firefox or Thunderbird and the version is in the affected range from step 1
  3. Check if JIT compilation is enabled in Firefox
    In Firefox address bar, type about:config and press Enter. In the search field, type javascript.options.jit to find the JIT preference. If set to true, JIT is enabled
    Affected if The javascript.options.jit preference is set to true (enabled) and version is affected
  4. Check if JIT compilation is enabled in Thunderbird
    In Thunderbird, go to Edit > Preferences > Advanced > Config Editor (or type config-editor in the search). Search for javascript.options.jit preference
    Affected if The javascript.options.jit preference is set to true (enabled) and version is affected

You are affected if running Firefox or Thunderbird version below 140.6.0 (ESR) or below 146.0 (regular) with the JIT compiler enabled.

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 Firefox to version 146 or later, Firefox ESR to 140.6 or later, Thunderbird to 146 or later, or Thunderbird ESR to 140.6 or later. Apply via standard software update mechanisms.

Recommended fix High confidence

Firefox 146 or Firefox ESR 140.6; Thunderbird 146 or Thunderbird 140.6

  1. Check current Firefox version by navigating to Help > About Firefox (or menu > Firefox > About Firefox)
  2. Check current Thunderbird version by navigating to Help > About Thunderbird (or menu > Thunderbird > About Thunderbird)
  3. For Firefox: Download Firefox 146 or Firefox ESR 140.6 from the official Mozilla website (www.mozilla.org)
  4. For Thunderbird: Download Thunderbird 146 or Thunderbird 140.6 from the official Mozilla website
  5. Close all running instances of Firefox or Thunderbird
  6. Run the downloaded installer and follow the prompts to complete the upgrade
  7. Restart the application after the upgrade completes
Caveat Standard security update with no major breaking changes expected

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
  • Testing4.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,340
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,144.

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-2025-14330 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