FirefoxWeb browser · Mozilla
CVE-2024-9398
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 · uneditedBy checking the result of calls to `window.open` with specifically set protocol handlers, an attacker could determine if the application which implements that protocol handler is installed. 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 · high confidenceA vulnerability in Firefox and Thunderbird allows malicious web pages to enumerate installed applications by exploiting `window.open()` with protocol handlers. The browser's response to these calls reveals whether a specific protocol handler (and thus the associated application) is installed on the system, enabling targeted reconnaissance.
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
< 131.0
Firefox EsrWeb browser
< 128.3.0< 128.3= 129.0CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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 checksWork through these to decide whether this CVE applies to you.
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Check Firefox versionNavigate to Firefox menu > Help > About Firefox (or enter 'about:support' in address bar). Note the version number displayed.Affected if Version is below 131.0 (for regular Firefox) or below 128.3.0 (for Firefox ESR)
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Check Thunderbird versionNavigate to Thunderbird menu > Help > About Thunderbird. Note the version number displayed.Affected if Version is below 128.3.0, or version is exactly 129.0
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Verify web browsing is enabledConfirm the product is used for web browsing or email with HTML content rendering, as the attack requires loading malicious web pages.Affected if Web browsing or HTML email rendering is enabled and the browser can load arbitrary web content
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Confirm protocol handler exposureTest whether a web page can trigger window.open() with a custom protocol (such as 'myapp://') and observe if the browser returns a valid window or an error, indicating whether the handler exists.Affected if The browser allows web pages to detect presence of custom protocol handlers without user interaction
You are affected if you run Firefox below 131.0 (or ESR below 128.3.0) or Thunderbird below 128.3.0 or exactly 129.0, and use the product to browse web pages or view HTML email content.
Generated from the published advisory. Verify against your own configuration.
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 · scoped128.3128.3.0131.0
Update affected products to Firefox 131+, Firefox ESR 128.3+, or Thunderbird 128.3+/131+ to patch the protocol handler enumeration vector.
Firefox 131.0+, Firefox ESR 128.3.0+, Thunderbird 128.3+ or 131+
- Upgrade Firefox to version 131.0 or later
- Upgrade Firefox ESR to version 128.3.0 or later
- Upgrade Thunderbird to version 128.3 or later, or version 131 or later
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
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
Free · runs locallyCheck whether your project pulls in CVE-2024-9398 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2024-9398 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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
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