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FirefoxWeb browser · Mozilla

CVE-2024-3856

HIGH · 8.8 CVSS v3.1 Published 2024-04-16
Fix available
A fix is available. Upgrade to 125.0 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

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 · unedited
A use-after-free could occur during WASM execution if garbage collection ran during the creation of an array. 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 confidence

A use-after-free vulnerability exists in Firefox's WebAssembly runtime where garbage collection can trigger during array creation, potentially freeing memory that is still being accessed by WASM code. This memory safety flaw could allow arbitrary code execution.

MitigationUpgrade Firefox to version 125 or later. No further client-side remediation is required for this browser vulnerability.

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
Affected:< 125.0

CVSS 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
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check Firefox version number
    Navigate to Menu > Help > About Firefox, or enter 'about:support' in the address bar to view the version number under 'Application Basics'
    Affected if The installed version is earlier than 125.0 (for example 124.x, 124.0.1, etc.)
  2. Confirm WebAssembly runtime is enabled
    Enter 'about:config' in the address bar, search for 'javascript.options.wasm', and verify the value is set to true
    Affected if javascript.options.wasm is set to true (this is the default setting, making most users potentially affected if version check fails)

A user is affected if their Firefox version is earlier than 125.0 and WebAssembly remains enabled (the default state).

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Upgrade available Upgrade to 125.0 or later
Fixed in 125.0
Interim mitigation

Upgrade Firefox to version 125 or later. No further client-side remediation is required for this browser vulnerability.

Recommended fix High confidence

Firefox 125.0

  1. Check current Firefox version by navigating to about:support or going to Help > About Firefox
  2. Download Firefox 125.0 or later from the official Mozilla website (www.mozilla.org)
  3. Install the updated Firefox version
  4. Restart Firefox to complete the update
Caveat Browser updates typically have minimal breaking changes; however, some older extensions may need updates for compatibility with the new version.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
3.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

Scan for this in your stack

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dbcve dependency scanner

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-3856 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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