FirefoxWeb browser · Mozilla
CVE-2026-4725
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 149 and Thunderbird 149.
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 use-after-free vulnerability in the Graphics: Canvas2D component allows an attacker to escape the browser sandbox and execute arbitrary code with elevated privileges. The memory corruption occurs when the Canvas2D rendering engine improperly handles object lifecycle, potentially enabling a remote attacker to achieve code execution outside the sandboxed environment.
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
< 149.0CVSS 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
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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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Verify Firefox is installedCheck for Firefox executable in typical installation paths: Windows: C:\Program Files\Mozilla Firefox\firefox.exe, Linux: /usr/bin/firefox or /opt/firefox/firefox, macOS: /Applications/Firefox.appAffected if Firefox is present on the system
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Retrieve installed Firefox versionRun firefox --version from command line, or on Windows right-click firefox.exe > Properties > Details > File version, or navigate to Firefox > Help > About FirefoxAffected if Unable to determine version or version shows as < 149.0
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Compare against affected version rangeCompare the installed version number to the affected range: versions prior to 149.0 are vulnerableAffected if Installed version is below 149.0 (for example, 148.x, 148.0.1, 147.x, etc.)
If Firefox is installed and the version is below 149.0, the environment is affected by this vulnerability.
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 · scoped149.0
Update Firefox to version 149 or later, and Thunderbird to version 149 or later. Prioritize updates on systems with direct internet exposure or where these applications handle untrusted content.
Firefox 149.0 (or Thunderbird 149.0 if using Thunderbird)
- Upgrade Firefox to version 149.0 or later by checking for updates in the application menu (Help > About Firefox) or downloading from the official Mozilla website
- If using Thunderbird, upgrade Thunderbird to version 149.0 or later via the same method
- After upgrading, verify the version by navigating to Help > About to confirm the installed version is 149.0 or higher
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
- 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 $1,424.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-4725 — 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-2026-4725 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