FirefoxWeb browser · Mozilla
CVE-2019-11691
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 · uneditedA use-after-free vulnerability can occur when working with XMLHttpRequest (XHR) in an event loop, causing the XHR main thread to be called after it has been freed. This results in a potentially exploitable crash. This vulnerability affects Thunderbird < 60.7, Firefox < 67, and Firefox ESR < 60.7.
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 use-after-free vulnerability in XMLHttpRequest (XHR) allows the XHR main thread to be invoked after it has been freed during event loop processing, causing a potentially exploitable crash.
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
< 67.0
Firefox EsrWeb browser
< 60.7< 60.7CVSS 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
- High
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/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 checksWork through these to decide whether this CVE applies to you.
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Identify the installed Mozilla productCheck which Mozilla application is installed by looking for firefox, firefox-esr, or thunderbird in the system or examining the application's About/Help sectionAffected if Any of Firefox, Firefox ESR, or Thunderbird is installed
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Determine the installed versionRun the application and navigate to Help > About, or check the version via command line (e.g., firefox --version, thunderbird --version)Affected if The version cannot be determined or is below the affected thresholds
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Compare against affected Firefox versionsIf Firefox is installed, compare the version to 67.0 (note: 67.0 itself is not affected, only versions below it)Affected if Firefox version is less than 67.0
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Compare against affected Firefox ESR versionsIf Firefox ESR is installed, compare the version to 60.7 (note: 60.7 itself is not affected, only versions below it)Affected if Firefox ESR version is less than 60.7
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Compare against affected Thunderbird versionsIf Thunderbird is installed, compare the version to 60.7 (note: 60.7 itself is not affected, only versions below it)Affected if Thunderbird version is less than 60.7
The environment is affected if Mozilla Firefox is below 67.0, Firefox ESR is below 60.7, or Thunderbird is below 60.7, since the use-after-free in XMLHttpRequest only impacts those version ranges.
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 · scoped60.767.0
Update to Firefox 67+, Firefox ESR 60.7+, or Thunderbird 60.7+ to remediate this vulnerability.
Firefox 67.0, Firefox ESR 60.7, or Thunderbird 60.7
- Upgrade Firefox to version 67.0 or later
- Upgrade Firefox ESR to version 60.7 or later
- Upgrade Thunderbird to version 60.7 or later
- After upgrading, verify the installation by checking the application version in Help > About
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-2019-11691 — 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-2019-11691 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
- No spam, self-promotion, credentials, or personal data