FirefoxWeb browser · Mozilla
CVE-2021-23981
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 · uneditedA texture upload of a Pixel Buffer Object could have confused the WebGL code to skip binding the buffer used to unpack it, resulting in memory corruption and a potentially exploitable information leak or crash. This vulnerability affects Firefox ESR < 78.9, Firefox < 87, and Thunderbird < 78.9.
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 · high confidenceA texture upload of a Pixel Buffer Object (PBO) in WebGL can cause the WebGL code to skip binding the buffer used to unpack it, leading to memory corruption and potentially exploitable information leaks or crashes in affected Firefox ESR, Firefox, and Thunderbird versions prior to the patched releases.
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
< 87.0
Firefox EsrWeb browser
< 78.9< 78.9CVSS 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
- High
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/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 checksWork through these to decide whether this CVE applies to you.
-
Identify the Mozilla product and versionOpen the application and navigate to: Firefox: Help > About Firefox; Firefox ESR: Help > About Firefox ESR; Thunderbird: Help > About Thunderbird. Record the version number shown.Affected if The product is Firefox version below 87.0, Firefox ESR version below 78.9, or Thunderbird version below 78.9.
-
Confirm WebGL is enabledIn Firefox: type 'about:support' in the address bar and look for the WebGL Driver Renderer entry. In Thunderbird: compose a new message, insert an image, and check if WebGL context can be created via browser developer tools.Affected if WebGL is enabled and functional in the browser. If WebGL is completely disabled, the vulnerability cannot be triggered.
-
Check for WebGL context usageVisit a WebGL-enabled website or use the browser developer tools (F12) to create a WebGL context and verify PBO (PIXEL_UNPACK_BUFFER) functionality is available.Affected if WebGL with Pixel Buffer Object support is actively being used. The flaw only triggers during PBO texture upload operations.
You are affected if you run Firefox below 87.0, Firefox ESR below 78.9, or Thunderbird below 78.9 AND you have WebGL enabled AND you use WebGL applications that perform Pixel Buffer Object texture uploads.
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.
From vendor data78.987.0
Upgrade to Firefox ESR 78.9+, Firefox 87+, or Thunderbird 78.9+ to patch the WebGL buffer binding vulnerability.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 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 $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-23981 — 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-2021-23981 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