FirefoxWeb browser · Mozilla
CVE-2020-12407
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 · uneditedMozilla Developer Nicolas Silva found that when using WebRender, Firefox would under certain conditions leak arbitrary GPU memory to the visible screen. The leaked memory content was visible to the user, but not observable from web content. This vulnerability affects Firefox < 77.
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 WebRender (Firefox's GPU rendering pipeline), the browser would under certain conditions leak arbitrary GPU memory contents directly to the visible screen. This memory leak was visible to the end user but was not observable or accessible from web content, limiting the exploitation vector to local screen observation only.
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
< 77.0CVSS 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
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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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Check Firefox versionNavigate to Menu > Help > About Firefox, or enter 'about:support' in the address bar to view the version numberAffected if The version displayed is earlier than 77.0 (for example, 76.x or earlier)
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Confirm WebRender is the active rendererIn 'about:support', locate the 'Compositing' row under 'Graphics' section. Look for 'WebRender' as the active compositorAffected if WebRender is listed as the active compositor (the vulnerability only applies when WebRender is enabled)
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Check for WebRender flag in about:configEnter 'about:config' in the address bar, search for 'webrender.enabled', and verify the boolean valueAffected if The preference 'webrender.enabled' is set to true (note: on some versions, WebRender may be force-enabled via this flag)
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Identify the graphics driverIn 'about:support', check the 'Graphics' section for the Driver Vendor and Driver Version under 'GPU #1'Affected if Running on a system with a GPU that supports WebRender (most modern GPUs do), combined with Firefox < 77 with WebRender enabled
A user is affected if they are running Firefox version 76.x or earlier with WebRender enabled as the compositor, causing arbitrary GPU memory to potentially leak to the screen.
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 data77.0
Upgrade Firefox to version 77 or later to remediate this WebRender GPU memory leak vulnerability.
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-2020-12407 — 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-2020-12407 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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