FirefoxWeb browser · Mozilla
CVE-2020-6821
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 · uneditedWhen reading from areas partially or fully outside the source resource with WebGL's <code>copyTexSubImage</code> method, the specification requires the returned values be zero. Previously, this memory was uninitialized, leading to potentially sensitive data disclosure. This vulnerability affects Thunderbird < 68.7.0, Firefox ESR < 68.7, and Firefox < 75.
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 confidenceWhen using WebGL's copyTexSubImage method to read from areas partially or fully outside the source resource, the specification requires returning zero values. However, the memory was left uninitialized, potentially exposing sensitive data from previously allocated memory regions.
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
< 75.0
Firefox EsrWeb browser
< 68.7.0< 68.7.0CVSS 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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Identify installed Mozilla productCheck if Firefox, Firefox ESR, or Thunderbird is installed by looking for the application in system programs or checking the version via command line (e.g., firefox --version, thunderbird --version)Affected if Any of these products are installed
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Check installed Firefox versionRun 'firefox --version' or look at Firefox > Help > About FirefoxAffected if Version is below 75.0 (for regular Firefox)
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Check installed Firefox ESR versionRun 'firefox --version' or look at Firefox ESR > Help > About Firefox ESR - the ESR version will appear in the window titleAffected if Version is below 68.7.0
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Check installed Thunderbird versionRun 'thunderbird --version' or look at Thunderbird > Help > About ThunderbirdAffected if Version is below 68.7.0
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Verify WebGL is accessibleIn Firefox, type 'about:support' in the address bar and search for 'WebGL' in the Graphics section, or visit a WebGL test siteAffected if WebGL is enabled and functional in the browser
User is affected if they have an unpatched version (Firefox < 75.0, Firefox ESR < 68.7.0, or Thunderbird < 68.7.0) WITH WebGL enabled and in use.
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 data68.7.075.0
Update affected products to patched versions: Thunderbird to 68.7.0 or later, Firefox ESR to 68.7 or later, Firefox to 75 or later. This is typically handled via standard software update mechanisms.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 h
- Testing1.0 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 $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-6821 — 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-2020-6821 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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