FirefoxWeb browser · Mozilla
CVE-2021-23994
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 WebGL framebuffer was not initialized early enough, resulting in memory corruption and an out of bound write. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.
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 confidenceA WebGL framebuffer is not initialized early enough in the rendering pipeline, causing memory corruption and an out-of-bounds write vulnerability. This memory safety issue in Firefox and Thunderbird's WebGL implementation can be triggered by malicious web content.
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
< 88.0
Firefox EsrWeb browser
< 78.10< 78.10CVSS 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
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 checksWork through these to decide whether this CVE applies to you.
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Check your Firefox or Thunderbird versionIn Firefox: type 'about:support' in the address bar and look at the 'Version' field. In Thunderbird: go to Help > About to see the version number.Affected if The version is below 88.0 for Firefox, below 78.10 for Firefox ESR, or below 78.10 for Thunderbird.
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Verify WebGL is enabledType 'about:config' in the Firefox address bar, accept the warning, then search for 'webgl.disabled'. Check if the value is set to 'true' or 'false'.Affected if WebGL is enabled (webgl.disabled is false or not present). If WebGL is disabled, the vulnerability cannot be triggered.
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Confirm WebGL is accessible to web contentIn about:config, verify that 'webgl.disabled' is set to false (or does not exist), and check 'webgl.enable-extensions' is not forcing a block. You can also visit a WebGL test site to confirm WebGL functions in your browser.Affected if WebGL is functional and accessible to websites. The flaw requires WebGL to be functional for exploitation.
You are affected if your installed version is Firefox below 88.0, Firefox ESR below 78.10, or Thunderbird below 78.10 AND WebGL is enabled and functional in your browser.
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 · scoped78.1088.0
Upgrade to Firefox 88+, Thunderbird 78.10+, or Firefox ESR 78.10+ to patch the improper framebuffer initialization timing.
Firefox 88.0, Firefox ESR 78.10, or Thunderbird 78.10 (depending on product)
- Upgrade Firefox to version 88.0 or later
- Upgrade Firefox ESR to version 78.10 or later
- Upgrade Thunderbird to version 78.10 or later
- After upgrading, verify the WebGL functionality works correctly in the browser
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation3.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-23994 — 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-2021-23994 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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- 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
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