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FirefoxWeb browser · Mozilla

CVE-2024-7520

HIGH · 8.8 CVSS v3.1 Published 2024-08-06
Fix available
A fix is available. Upgrade to 128.1.0 / 129.0 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 type confusion bug in WebAssembly could be leveraged by an attacker to potentially achieve code execution. This vulnerability affects Firefox < 129, Firefox ESR < 128.1, and Thunderbird < 128.1.

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 confidence

A type confusion vulnerability in Mozilla's WebAssembly engine allows attackers to potentially execute arbitrary code by exploiting improper type handling during Wasm execution. This is a memory safety flaw that could enable controlled memory corruption leading to code execution.

MitigationApply vendor updates: upgrade Firefox to version 129+, Firefox ESR to 128.1+, or Thunderbird to 128.1+. Deploy via enterprise patch management or manual update for end-user systems.

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:< 129.0
Firefox EsrWeb browser
Affected:< 128.1.0
ThunderbirdApplication
Affected:< 128.1.0

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. Identify installed Mozilla product
    Open the application and check Help > About, or on Windows check Add/Remove Programs, or on Linux run: dpkg -l | grep -E 'firefox|thunderbird' or rpm -qa | grep -E 'firefox|thunderbird'
    Affected if any Firefox or Thunderbird installation is present
  2. Check Firefox version
    In Firefox, navigate to about:firefox or go to Help > About Firefox. On command line: firefox --version
    Affected if version is less than 129.0 (or any ESR version less than 128.1.0) if running Firefox
  3. Check Firefox ESR version
    In Firefox ESR, navigate to about:firefox or go to Help > About Firefox. On command line: firefox --version
    Affected if version is less than 128.1.0 if running Firefox ESR
  4. Check Thunderbird version
    In Thunderbird, go to Help > About Thunderbird. On command line: thunderbird --version
    Affected if version is less than 128.1.0 if running Thunderbird

You are affected if any installed Firefox (including ESR) is below version 128.1.0, or any standard Firefox is below 129.0, or Thunderbird is below version 128.1.0, and WebAssembly content is processed.

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 128.1.0 / 129.0 or later
Fixed in 128.1.0129.0
Interim mitigation

Apply vendor updates: upgrade Firefox to version 129+, Firefox ESR to 128.1+, or Thunderbird to 128.1+. Deploy via enterprise patch management or manual update for end-user systems.

Recommended fix High confidence

Firefox 129.0, Firefox ESR 128.1.0, Thunderbird 128.1.0

  1. Check your current Firefox version by navigating to Help > About Firefox
  2. Check your current Firefox ESR version by navigating to Help > About Firefox
  3. Check your current Thunderbird version by navigating to Help > About Thunderbird
  4. For Firefox: Update to version 129.0 or later via Help > Check for Updates
  5. For Firefox ESR: Update to version 128.1.0 or later via Help > Check for Updates
  6. For Thunderbird: Update to version 128.1.0 or later via Help > Check for Updates
  7. Alternatively, download the latest versions from the official Mozilla website: www.mozilla.org
  8. Restart the application after updating to apply the fix
Caveat Security updates typically have minimal risk; verify critical extensions/add-ons are compatible before production deployment

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
5.0 hours of engineering $890
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.

Scan for this in your stack

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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-2024-7520 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