FirefoxWeb browser · Mozilla
CVE-2026-6757
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 · uneditedInvalid pointer in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 150, 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 confidenceAn invalid pointer dereference vulnerability in the JavaScript WebAssembly component allows memory corruption, potentially leading to crash or arbitrary code execution. This appears to be a use-after-free or dangling pointer issue in the WebAssembly runtime or JIT compiler.
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 Mozilla productCheck for Firefox or Thunderbird by running: firefox --version or thunderbird --version on Linux/Mac, or checking Add/Remove Programs on WindowsAffected if Neither Firefox nor Thunderbird is installed - not applicable to this CVE
-
Determine exact Firefox versionRun 'firefox --version' or look at Help > About Firefox to get the full version numberAffected if Firefox version is less than 140.10.0 or less than 150.0 (both conditions indicate an affected version)
-
Determine exact Thunderbird versionRun 'thunderbird --version' or look at Help > About Thunderbird to get the full version numberAffected if Thunderbird version is 140.0 or higher but less than 140.10.0
-
Confirm WebAssembly is in useWebAssembly is enabled by default in Firefox and Thunderbird - check about:config for javascript.options.wasm (should be true by default)Affected if WebAssembly is disabled - the vulnerability requires WebAssembly to be enabled to trigger the flaw
User is affected if they have Firefox version less than 140.10.0 (or less than 150.0), or Thunderbird version 140.0 through 140.9.x, AND WebAssembly is enabled (default state).
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
Apply the vendor-supplied updates by upgrading to Firefox 150+, Firefox ESR 140.10+, Thunderbird 150+, or Thunderbird 140.10+ as appropriate.
Firefox 150.0+ / Firefox ESR 140.10+ / Thunderbird 140.10+ / Thunderbird 150+
- Check current Firefox or Thunderbird version via Help > About [Product Name]
- For Firefox: Update to version 150.0 or later, or update to Firefox ESR 140.10
- For Thunderbird: Update to version 140.10 or later, or update to Thunderbird 150
- Restart the application after updating
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
- 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 $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-6757 — 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-2026-6757 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