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FirefoxWeb browser · Mozilla

CVE-2025-0237

MEDIUM · 5.4 CVSS v3.1 Published 2025-01-07
Fix available
A fix is available. Upgrade to 128.6.0 / 134.0 or later.
See remediation →
60/100
Remediation priority · Elevated
Remotely reachable 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
The WebChannel API, which is used to transport various information across processes, did not check the sending principal but rather accepted the principal being sent. This could have led to privilege escalation attacks. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

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

The WebChannel API in Firefox and Thunderbird did not validate the sending principal, instead trusting and accepting whatever principal value was provided by the sender. This allowed attackers to spoof higher-privilege principals and achieve privilege escalation across process boundaries.

MitigationUpdate to Firefox 134, Firefox ESR 128.6, Thunderbird 134, or Thunderbird 128.6 or later to receive the patched version that validates the sending principal before accepting it.

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:< 128.6.0< 134.0
ThunderbirdApplication
Affected:< 128.6.0>= 129.0, < 134.0

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
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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. Check if Mozilla Firefox is installed
    Open Firefox and navigate to 'Help' > 'About Firefox', or enter 'about:support' in the address bar to view the version number
    Affected if Firefox version is present and is less than 128.6.0 or falls between 129.0 and 133.x (inclusive)
  2. Check if Mozilla Thunderbird is installed
    Open Thunderbird and navigate to 'Help' > 'About Thunderbird', or enter 'about:support' in the address bar to view the version number
    Affected if Thunderbird version is present and is less than 128.6.0 or falls between 129.0 and 133.x (inclusive)
  3. Compare installed version against affected ranges
    Review the version number obtained from the About page. For Firefox, any version below 134.0 is affected. For Thunderbird, any version below 128.6.0 or between 129.0 and 133.x is affected.
    Affected if The installed version is before 134.0 for either product

A user is affected if Firefox or Thunderbird is installed with any version prior to 134.0 (or 128.6.0 for Thunderbird's ESR branch), since the vulnerability exists in the WebChannel API principal validation of those versions.

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 128.6.0 / 134.0 or later
Fixed in 128.6.0134.0
Interim mitigation

Update to Firefox 134, Firefox ESR 128.6, Thunderbird 134, or Thunderbird 128.6 or later to receive the patched version that validates the sending principal before accepting it.

Recommended fix High confidence

Firefox 134 / Firefox ESR 128.6 / Thunderbird 134 / Thunderbird 128.6

  1. Check current Firefox or Thunderbird version via Menu > Help > About (or running 'firefox --version' or 'thunderbird --version' in terminal)
  2. Download Firefox 134 (or Firefox ESR 128.6 for enterprise/extended support) from https://www.mozilla.org/firefox/download/
  3. Or download Thunderbird 134 (or Thunderbird 128.6) from https://www.thunderbird.net/
  4. Close all Firefox/Thunderbird instances
  5. Install the downloaded version
  6. Restart the application and verify the new version is running
Caveat Mozilla stable releases typically have no breaking changes; this is a security update

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

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,800
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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-2025-0237 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