FirefoxWeb browser · Mozilla
CVE-2026-6762
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 · uneditedSpoofing issue in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
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 confidenceThis is a DOM-based spoofing vulnerability in Firefox and Thunderbird that allows attackers to manipulate the Document Object Model in ways that can deceive users about the true origin of content, potentially spoofing the address bar or other security indicators. The vulnerability exists in the DOM: Core & HTML component.
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
< 140.10.0< 150.0>= 140.0, < 140.10.0CVSS 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
- Required
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L
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.
-
Identify installed Firefox versionIn Firefox, go to Menu > Help > About Firefox (or navigate to about:support). The version number is displayed at the top.Affected if The version is below 140.10.0 or is between 140.10.0 and 149.x (i.e., less than 150.0)
-
Identify installed Thunderbird versionIn Thunderbird, go to Menu > Help > About Thunderbird. The version number is displayed at the top.Affected if The version is 140.0 or higher but below 140.10.0
-
Check for security updatesIn Firefox, go to Menu > Help > About Firefox to verify if you are running the latest version. In Thunderbird, check Menu > Help > About Thunderbird. Both should indicate whether updates are available.Affected if The application reports an available update to version 150 or higher (or 140.10+ for Thunderbird), indicating your current version is older and vulnerable
You are affected if you run Firefox version below 140.10.0, any Firefox version between 140.10.0 and 149.x, or Thunderbird version 140.0 through 140.9.x.
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 · scoped140.10.0150.0
Update affected software to the patched versions: Firefox 150+, Firefox ESR 115.35+, Firefox ESR 140.10+, Thunderbird 150+, or Thunderbird 140.10+.
Firefox 150 / Firefox ESR 140.10 / Thunderbird 140.10 or 150
- Verify current Firefox or Thunderbird version by navigating to Help > About (or typing 'about:support' in the address bar)
- Download the fixed version from the official Mozilla website (www.mozilla.org) or use the application's built-in update mechanism
- For Firefox: Upgrade to Firefox 150 or later, or Firefox ESR 140.10 (or ESR 115.35 for older ESR deployments)
- For Thunderbird: Upgrade to Thunderbird 140.10 or later, or Thunderbird 150
- Restart the application after the update completes
- Verify the update was successful by checking the version number in About
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 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 $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-6762 — 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-2026-6762 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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