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FirefoxWeb browser · Mozilla

CVE-2024-9396

HIGH · 8.8 CVSS v3.1 Published 2024-10-01
Fix available
A fix is available. Upgrade to 128.3.0 / 131.0 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
It is currently unknown if this issue is exploitable but a condition may arise where the structured clone of certain objects could lead to memory corruption. This vulnerability affects Firefox < 131, Firefox ESR < 128.3, Thunderbird < 128.3, and Thunderbird < 131.

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 memory corruption vulnerability exists in the structured clone algorithm used by Firefox and Thunderbird. When certain objects are cloned using the structured clone API, a condition can arise that leads to memory corruption, potentially allowing arbitrary code execution.

MitigationUpdate affected products to the patched versions: Firefox 131 or later, Firefox ESR 128.3 or later, Thunderbird 128.3 or later, or Thunderbird 131 or later.

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:< 128.3.0< 131.0
ThunderbirdApplication
Affected:< 128.3.0>= 129.0, < 131.0

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 terminal or file explorer and locate the Firefox or Thunderbird installation directory. On Windows check Program Files/Mozilla Firefox or Program Files/Mozilla Thunderbird. On macOS check /Applications/Firefox.app or /Applications/Thunderbird.app. On Linux check /usr/lib/firefox or /usr/lib/thunderbird.
    Affected if The installed product is Firefox or Thunderbird
  2. Get Firefox version number
    Launch Firefox, type 'about:firefox' in the address bar, and note the version shown. Alternatively on Windows right-click firefox.exe and select Properties > Details > File version. On Linux run 'firefox --version'. On macOS run '/Applications/Firefox.app/Contents/MacOS/firefox --version'.
    Affected if Firefox version is below 128.3.0 or between 128.3.0 and 130.x (inclusive) meaning below 131.0
  3. Get Thunderbird version number
    Launch Thunderbird, go to Help > About Thunderbird to see the version. On Windows right-click thunderbird.exe and select Properties > Details > File version. On Linux run 'thunderbird --version'. On macOS run '/Applications/Thunderbird.app/Contents/MacOS/thunderbird --version'.
    Affected if Thunderbird version is below 128.3.0 or between 129.0 and 130.x (inclusive) meaning below 131.0
  4. Verify structured clone usage
    This vulnerability is triggered through the structured clone algorithm. There is no simple configuration toggle to check. The flaw exists in the browser engine itself when certain objects are cloned. Only version checking determines exposure.
    Affected if The installed product is Firefox ESR (any version below 128.3.0) or Firefox (any version below 131.0) or Thunderbird (any version below 128.3.0 or between 129.0 and 130.x)

You are affected if Firefox is any version below 131.0, Firefox ESR is below 128.3.0, or Thunderbird is below 128.3.0 or between 129.0 and 130.x inclusive.

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 128.3.0 / 131.0 or later
Fixed in 128.3.0131.0
Interim mitigation

Update affected products to the patched versions: Firefox 131 or later, Firefox ESR 128.3 or later, Thunderbird 128.3 or later, or Thunderbird 131 or later.

Recommended fix High confidence

Firefox 131.0+, Firefox ESR 128.3.0+, Thunderbird 128.3.0+, Thunderbird 131.0+

  1. Check current Firefox version: Menu > Help > About Firefox
  2. Check current Thunderbird version: Menu > Help > About Thunderbird
  3. For Firefox: Download version 131.0 or later from https://www.mozilla.org/firefox/
  4. For Firefox ESR: Download version 128.3.0 or later from https://www.mozilla.org/firefox/
  5. For Thunderbird: Download version 131.0 or later (or 128.3.0 for older branch) from https://www.thunderbird.net/
  6. Install the updated version(s) and restart the application

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

Fix this in Firefox Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 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.

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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-2024-9396 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