FirefoxWeb browser · Mozilla
CVE-2024-3853
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 use-after-free could result if a JavaScript realm was in the process of being initialized when a garbage collection started. This vulnerability affects Firefox < 125.
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 race condition in Firefox's JavaScript engine allows a use-after-free when garbage collection runs while a JavaScript realm is being initialized. The GC can free memory that is still needed by the in-progress realm initialization, leading to dangling pointer dereference.
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
< 125.0CVSS 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
- Adjacent
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/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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Identify Firefox installation path and versionOn Windows: Check C:\Program Files\Mozilla Firefox\firefox.exe properties for version, or run 'firefox --version' in command prompt. On macOS: Run '/Applications/Firefox.app/Contents/MacOS/firefox --version' in Terminal. On Linux: Run 'firefox --version' or check via package manager with 'rpm -q firefox' or 'dpkg -l firefox'Affected if The version number returned is less than 125.0 (for example 124.0.1, 124.0, 123.0.7, etc.)
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Verify about:support version displayOpen Firefox, type 'about:support' in the address bar, and look for the 'Version' field in the 'Application Basics' sectionAffected if The version listed is any build prior to 125.0
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Confirm JavaScript execution environmentThe vulnerability triggers when JavaScript code executes in the browser - simply loading any web page with JavaScript content causes the JS engine to initialize and run garbage collectionAffected if Firefox is used to browse web content, which is the default behavior of the browser
You are affected if your Firefox installation shows a version number below 125.0, regardless of specific settings, since the race condition in the JS engine manifests during normal browser use with JavaScript content.
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 · scoped125.0
Upgrade Firefox to version 125 or later. Organizations should deploy the browser update through their patch management systems.
Firefox 125.0
- Open Firefox and navigate to Menu > Help > About Firefox to check the current version
- If the version is below 125.0, click 'Update to latest version' to initiate the automatic update
- Alternatively, download Firefox 125.0 or later from the official Mozilla website (www.mozilla.org)
- After updating, restart Firefox to complete the installation
- Verify the update by checking Help > About Firefox shows version 125.0 or higher
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 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 $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2024-3853 — 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-2024-3853 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
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