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FirefoxWeb browser · Mozilla

CVE-2025-9184

HIGH · 8.1 CVSS v3.1 Published 2025-08-19
Fix available
A fix is available. Upgrade to 140.2.0 / 142.0 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 140.1, Thunderbird ESR 140.1, Firefox 141 and Thunderbird 141. 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 142, Firefox ESR 140.2, Thunderbird 142, and Thunderbird 140.2.

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

Memory safety bugs in Firefox ESR 140.1, Thunderbird ESR 140.1, Firefox 141, and Thunderbird 141 caused memory corruption that could potentially be exploited for arbitrary code execution.

MitigationUpdate to Firefox 142 or Firefox ESR 140.2 (and Thunderbird 142 or Thunderbird 140.2 for Thunderbird installations).

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:< 140.2.0< 142.0
ThunderbirdApplication
Affected:< 140.2.0< 142.0

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
    Check for Firefox or Thunderbird installations: On Windows, look in Program Files or Program Files (x86). On macOS, check /Applications. On Linux, run 'which firefox thunderbird' or check /usr/bin/
    Affected if Either Firefox or Thunderbird is present on the system
  2. Check Firefox version
    Run 'firefox --version' in terminal, or go to Help > About Firefox in the application menu
    Affected if The version displayed is below 140.2.0 OR is version 141.x (below 142.0)
  3. Check Thunderbird version
    Run 'thunderbird --version' in terminal, or go to Help > About Thunderbird in the application menu
    Affected if The version displayed is below 140.2.0 OR is version 141.x (below 142.0)

A user is affected if Firefox is installed at a version below 140.2.0 or between 140.2.0 and 141.x (exclusive of 142.0), or if Thunderbird is at a version below 140.2.0 or between 140.2.0 and 141.x (exclusive of 142.0).

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 140.2.0 / 142.0 or later
Fixed in 140.2.0142.0
Interim mitigation

Update to Firefox 142 or Firefox ESR 140.2 (and Thunderbird 142 or Thunderbird 140.2 for Thunderbird installations).

Recommended fix High confidence

Firefox 142 (or Firefox ESR 140.2); Thunderbird 142 (or Thunderbird 140.2)

  1. 1. Back up any important data, bookmarks, and settings from your current Firefox or Thunderbird installation
  2. 2. Navigate to the official Mozilla download page at www.mozilla.org
  3. 3. Download the appropriate installer for your system: Firefox 142 or later, or Firefox ESR 140.2 or later
  4. 4. Alternatively, within the application, check for updates via Help > About Firefox/Thunderbird and follow prompts to update
  5. 5. Close all browser/mail windows before installing the update
  6. 6. Run the installer and follow the on-screen instructions to complete the upgrade
  7. 7. Restart the application after installation completes
  8. 8. Verify the installed version by checking Help > About to confirm you are on 142.x or 140.2.x
Caveat Minor: Some legacy extension compatibility may be affected; review add-on compatibility after upgrade

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

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-2025-9184 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