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FirefoxWeb browser · Mozilla

CVE-2024-9393

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://pdf.js` origin. This could allow them to access cross-origin PDF 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

Cross-origin data leak vulnerability in PDF.js where specially crafted multipart responses allow arbitrary JavaScript execution under the resource://pdf.js origin, enabling access to cross-origin PDF content. Android clients lack Site Isolation protections present in desktop builds, allowing full cross-origin access.

MitigationUpdate affected products to patched versions: Firefox 131+, Firefox ESR 115.16+, Firefox ESR 128.3+, or Thunderbird 128.3+/131+ depending on release track.

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 desktop, look in Applications or program files. On Android, check installed apps in Settings > Apps.
    Affected if The product is Mozilla Firefox or Thunderbird and the version falls within the affected ranges listed below.
  2. Check Firefox version number
    In Firefox, navigate to about:support or go to Menu > Help > About Firefox. The version is displayed on that page.
    Affected if Firefox version is below 131.0, OR between 116.0 and 128.3.0 (including 128.2.x), OR below 115.16.0 for ESR tracks.
  3. Check Thunderbird version number
    In Thunderbird, go to Menu > Help > About Thunderbird. The version is displayed on that page.
    Affected if Thunderbird version is below 128.3.0, or exactly 129.0.
  4. Verify PDF.js is in use
    PDF.js is the built-in PDF viewer. Open any PDF file in the browser or mail client, or attempt to view a PDF attachment in Thunderbird. Check if it loads using the internal PDF viewer.
    Affected if PDF.js processes the PDF file and the browser uses the resource://pdf.js origin.
  5. Check platform on Android
    On Android, verify the OS version in Settings > About Phone > Android version. Desktop builds have Site Isolation; Android builds do not.
    Affected if Running Firefox on Android and viewing cross-origin PDF content allows the full exploit.

A user is affected if they run Firefox < 131.0, Firefox ESR < 115.16.0 or 116.0-128.3.0, or Thunderbird < 128.3 or exactly 129.0, and view PDF files using the built-in PDF.js viewer, with Android being particularly vulnerable due to missing Site Isolation.

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

Update affected products to patched versions: Firefox 131+, Firefox ESR 115.16+, Firefox ESR 128.3+, or Thunderbird 128.3+/131+ depending on release track.

Recommended fix High confidence

Firefox 131.0+ | Firefox ESR 115.16.0+ / 128.3.0+ | Thunderbird 128.3.0+ / 131.0+

  1. 1. Identify the installed Firefox, Firefox ESR, or Thunderbird version by navigating to Menu > Help > About (or typing 'about:support' in the address bar)
  2. 2. For Firefox users: Upgrade to version 131.0 or later by visiting https://www.mozilla.org/firefox/ and downloading the latest release
  3. 3. For Firefox ESR users: If on ESR 115.x branch, upgrade to 115.16.0 or later; if on ESR 128.x branch, upgrade to 128.3.0 or later
  4. 4. For Thunderbird users: Upgrade to version 128.3.0 or later, or 131.0 or later
  5. 5. After upgrade, restart the application to complete the update
  6. 6. Verify the fix by checking Menu > Help > About to confirm the version number matches a fixed release
Caveat Standard upgrade with no expected breaking changes; ensure any legacy browser extensions are compatible

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
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

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-2024-9393 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