FirefoxWeb browser · Mozilla
CVE-2025-10527
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 · uneditedSandbox escape due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 143, Firefox ESR 140.3, Thunderbird 143, and Thunderbird 140.3.
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 use-after-free vulnerability in the Graphics: Canvas2D component of Firefox and Thunderbird allows an attacker to escape the browser sandbox and potentially execute arbitrary code via 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
< 140.3.0<= 143.0< 140.3.0>= 141.0, < 143.0CVSS 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
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/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.
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Identify installed Mozilla productRun 'firefox --version' or 'thunderbird --version' from command line, or check the application in Add/Remove Programs (Windows) or package manager (Linux)Affected if Either Firefox or Thunderbird is installed
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Determine exact Firefox versionRun 'firefox --version' or navigate to 'about:Firefox' in the browser address barAffected if Version is less than 140.3.0 OR version is 143.0 or lower (any version <= 143.0)
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Determine exact Thunderbird versionRun 'thunderbird --version' or check Help > About ThunderbirdAffected if Version is less than 140.3.0 OR version is 141.0 through 142.x (any version >= 141.0 and < 143.0)
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Confirm Canvas2D is in useNo additional check needed - the Graphics: Canvas2D component is enabled by default in Firefox and Thunderbird and is used whenever web pages render 2D graphics via HTML5 Canvas APIAffected if The affected product version is running and can render web content
If Firefox version is < 140.3.0 or <= 143.0, or Thunderbird version is < 140.3.0 or between 141.0 and < 143.0, the environment is affected by this use-after-free vulnerability in the Canvas2D component.
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 · scoped140.3.0143.0
Update Mozilla products to the fixed versions: Firefox 143, Firefox ESR 140.3, Thunderbird 143, or Thunderbird 140.3.
Firefox 143.0 / Firefox ESR 140.3 / Thunderbird 143.0 / Thunderbird ESR 140.3
- Check current Firefox or Thunderbird version by navigating to Help > About (or using 'firefox --version' / 'thunderbird --version' in terminal)
- For Firefox: Upgrade to version 143.0 or later
- For Firefox ESR: Upgrade to version 140.3 or later
- For Thunderbird: Upgrade to version 143.0 or later
- For Thunderbird ESR: Upgrade to version 140.3 or later
- Restart the application after upgrade
- Verify the fix by checking Help > About shows the corrected version number
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 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 $1,664.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-10527 — 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-2025-10527 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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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