FirefoxWeb browser · Mozilla
CVE-2021-43545
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 · uneditedUsing the Location API in a loop could have caused severe application hangs and crashes. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.
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 denial-of-service vulnerability in the Mozilla Location API where using the geolocation function in a loop causes severe application hangs and crashes, affecting Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.
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
< 95.0
Firefox EsrWeb browser
< 91.4.0
Debian LinuxOperating system
= 9.0= 10.0= 11.0< 91.4.0CVSS 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
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/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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Check Firefox versionOpen Firefox, go to Help > About Firefox, or run 'firefox --version' from command line, or check package manager: 'dpkg -l | grep firefox' or 'rpm -qa | grep firefox'Affected if Version is below 95.0
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Check Firefox ESR versionOpen Firefox ESR, go to Help > About Firefox ESR, or run 'firefox-esr --version' from command line, or check package manager: 'dpkg -l | grep firefox-esr' or 'rpm -qa | grep firefox-esr'Affected if Version is below 91.4.0
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Check Thunderbird versionOpen Thunderbird, go to Help > About Thunderbird, or run 'thunderbird --version' from command line, or check package manager: 'dpkg -l | grep thunderbird' or 'rpm -qa | grep thunderbird'Affected if Version is below 91.4.0
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Identify geolocation usage in applicationsSearch application source code or logs for repeated calls to navigator.geolocation.getCurrentPosition or navigator.geolocation.watchPosition within loops or rapid invocationsAffected if Geolocation function is being called in a loop or rapidly repeated manner in any custom or third-party application using the Mozilla location API
You are affected if any installed Firefox version is below 95.0, Firefox ESR is below 91.4.0, or Thunderbird is below 91.4.0 AND the geolocation feature is being actively used in a loop or repeated fashion.
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 · scoped91.4.095.0
Update affected Mozilla products to version 91.4.0 or higher (Thunderbird, Firefox ESR) or Firefox 95+. For enterprise deployments, use patch management to roll out the updates across all affected workstations.
Firefox 95.0+, Firefox ESR 91.4.0+, Thunderbird 91.4.0+
- Open Firefox/Thunderbird and navigate to Help > About [Application Name]
- Click 'Check for Updates' or allow the application to automatically check for updates
- Download and install the latest version (Firefox 95.0+ or Thunderbird 91.4.0+)
- Restart the application to complete the update
- Alternatively, download the latest version from the official Mozilla website and reinstall
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Firefox
Scoped from the published advisory
- Consultation2.0 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 $1,744.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-43545 — 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-2021-43545 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