FirefoxWeb browser · Mozilla
CVE-2024-3857
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 · uneditedThe JIT created incorrect code for arguments in certain cases. This led to potential use-after-free crashes during garbage collection. This vulnerability affects Firefox < 125, Firefox ESR < 115.10, and Thunderbird < 115.10.
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 JIT compiler bug in Firefox and Thunderbird generates incorrect code for function arguments in edge cases, leading to memory being freed while still referenced. This creates a use-after-free condition during garbage collection that can be triggered by specific JavaScript code patterns.
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
< 115.10< 125.0
Debian LinuxOperating system
= 10.0< 115.10CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/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 installed Firefox versionIn Firefox, navigate to Menu > Help > About Firefox, or enter 'about:support' in the address bar and look for the version number in the Application Basics sectionAffected if Version is below 115.10 or falls between 115.10 and 125.0 (exclusive)
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Identify installed Thunderbird versionIn Thunderbird, go to Menu > Help > About Thunderbird to display the version numberAffected if Version is below 115.10
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Verify if JIT compiler is enabledIn Firefox address bar, enter 'about:config', search for 'javascript.options.jit' and check if it is set to trueAffected if The JIT compiler is enabled (set to true) - the vulnerability only affects systems with JIT active
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Check if untrusted JavaScript can executeReview browser extension permissions and website scripting policies. This vulnerability is triggered by specific JavaScript code patterns during garbage collectionAffected if User can run arbitrary or untrusted JavaScript code in the browser (common for web browsing)
User is affected if running Firefox below 115.10 or between 115.10-124.x, Thunderbird below 115.10, and the JIT compiler is enabled in the browser settings.
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 · scoped115.10125.0
Upgrade affected installations to Firefox 125+, Firefox ESR 115.10+, or Thunderbird 115.10+ to receive the patched JIT compiler. No configuration changes or workarounds are available.
Firefox 125+ / Firefox ESR 115.10+ / Thunderbird 115.10+
- Check current Firefox or Thunderbird version via Help > About
- Back up browser profile data (stored in ~/.mozilla or ~/.thunderbird)
- For Firefox: Upgrade to Firefox 125 or later (or Firefox ESR 115.10 or later)
- For Thunderbird: Upgrade to Thunderbird 115.10 or later
- Restart the application after upgrade
- Verify the new version is installed via Help > About
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
- 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-2024-3857 — 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-2024-3857 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
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