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FirefoxWeb browser · Mozilla

CVE-2024-9394

HIGH · 7.5 CVSS v3.1 Published 2024-10-01
Fix available
A fix is available. Upgrade to 115.16.0 / 128.3 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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
An attacker could, via a specially crafted multipart response, execute arbitrary JavaScript under the `resource://devtools` origin. This could allow them to access cross-origin JSON content. This access is limited to "same site" documents by the Site Isolation feature on desktop clients, but full cross-origin access is possible on Android versions. This vulnerability affects Firefox < 131, Firefox ESR < 128.3, Firefox ESR < 115.16, 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 · high confidence

This is a cross-site scripting (XSS) vulnerability in Firefox and Thunderbird where a specially crafted multipart response allows arbitrary JavaScript execution under the `resource://devtools` origin, enabling access to cross-origin JSON content. While desktop clients are partially protected by Site Isolation (limited to same-site documents), Android versions allow full cross-origin access.

MitigationUpgrade Firefox to version 131 or later, Firefox ESR to 128.3+/115.16+, and Thunderbird to 128.3+/131+ to remediate this 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:< 131.0
Firefox EsrWeb browser
Affected:< 115.16.0>= 116.0, < 128.3.0
ThunderbirdApplication
Affected:< 128.3= 129.0

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
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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 the installed product
    Check if Mozilla Firefox or Thunderbird is installed on the system. In Firefox, navigate to 'about:support' or go to Help > About Firefox. In Thunderbird, go to Help > About Thunderbird.
    Affected if The product is Firefox or Thunderbird
  2. Determine the Firefox version
    In Firefox, type 'about:support' in the address bar or go to Help > About Firefox. Note the version number displayed (e.g., 130.0.3, 115.15.0, 128.2.0).
    Affected if Firefox version is less than 131.0, or is between 116.0 and 128.2.x inclusive, or is less than 115.16.0 for ESR branches
  3. Determine the Thunderbird version
    In Thunderbird, go to Help > About Thunderbird. Note the version number displayed (e.g., 128.2.0, 129.0).
    Affected if Thunderbird version is less than 128.3 or equals 129.0 exactly
  4. Check if this is Firefox for Android
    On Android devices, verify the Firefox installation by checking the app version in the Google Play Store or device Settings > Apps > Firefox. Android versions have full cross-origin access exploitation capability.
    Affected if The affected Firefox version is running on Android, which allows full cross-origin access rather than limited same-site access
  5. Confirm devtools accessibility
    The vulnerability requires the resource://devtools origin to be accessible. In Firefox, verify if DevTools have been used or if the browser profile has devtools enabled by default. No additional configuration check is needed as this is enabled by default in affected versions.
    Affected if DevTools are accessible in the browser (enabled by default in all standard installations)

A user is affected if they are running any Firefox version below 131.0, Firefox ESR below 115.16.0 or between 116.0 and 128.2.x, or Thunderbird below 128.3 or exactly 129.0, with the Android platform being the most severely impacted.

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 115.16.0 / 128.3 / 128.3.0 or later
Fixed in 115.16.0128.3128.3.0
Interim mitigation

Upgrade Firefox to version 131 or later, Firefox ESR to 128.3+/115.16+, and Thunderbird to 128.3+/131+ to remediate this vulnerability.

Recommended fix High confidence

Firefox 131.0+ | Firefox ESR 128.3.0+ (or 115.16.0+) | Thunderbird 128.3+

  1. Upgrade Firefox to version 131.0 or later
  2. Upgrade Firefox ESR 128.x to version 128.3.0 or later
  3. Upgrade Firefox ESR 115.x to version 115.16.0 or later
  4. Upgrade Thunderbird to version 128.3 or later (or 131.0 for Thunderbird 129.x users)

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.

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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-2024-9394 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