FirefoxWeb browser · Mozilla
CVE-2026-4712
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 · uneditedInformation disclosure in the Widget: Cocoa component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
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 confidenceAn information disclosure vulnerability exists in the Cocoa widget component of Firefox and Thunderbird. The Cocoa widget handles macOS native UI rendering. This flaw allows potentially sensitive information to be disclosed, likely through the browser's handling of native macOS UI elements or rendering pipeline. The vulnerability was addressed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
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
< 140.9.0< 149.0CVSS 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
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Confirm macOS platformVerify the system is running macOS (this vulnerability affects only the Cocoa widget component used on macOS)Affected if Running on macOS with Firefox or Thunderbird installed
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Check Firefox versionOpen Firefox, click Firefox menu > About Firefox. Alternatively, run: /Applications/Firefox.app/Contents/MacOS/firefox --versionAffected if Version is earlier than 149.0 (regular Firefox) or earlier than 140.9.0 (Firefox ESR)
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Check Thunderbird versionOpen Thunderbird, click Thunderbird menu > About Thunderbird. Alternatively, run: /Applications/Thunderbird.app/Contents/MacOS/thunderbird --versionAffected if Version is earlier than 149.0 (regular Thunderbird) or earlier than 140.9.0 (Thunderbird ESR)
User is affected if running Firefox < 149.0, Firefox ESR < 140.9.0, Thunderbird < 149.0, or Thunderbird ESR < 140.9.0 on macOS.
Generated from the published advisory. Verify against your own configuration.
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 · scoped140.9.0149.0
Upgrade to Firefox 149 (or ESR 140.9) and Thunderbird 149 (or 140.9) or later to remediate this vulnerability. Organizations should test the updated versions for compatibility with existing configurations.
Firefox 149 (or Firefox ESR 140.9 for ESR users)
- Upgrade Firefox to version 149 or later for the 149.x branch
- For Firefox ESR users, upgrade to Firefox ESR 140.9 or later
- Verify the upgrade by checking Help > About Firefox (or About Thunderbird for Thunderbird users)
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation1.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,936.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-4712 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-4712 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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