FirefoxWeb browser · Mozilla
CVE-2021-29965
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 malicious website that causes an HTTP Authentication dialog to be spawned could trick the built-in password manager to suggest passwords for the currently active website instead of the website that triggered the dialog. *This bug only affects Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects Firefox < 89.
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 for Android allows a malicious website to spawn an HTTP Authentication dialog that tricks the built-in password manager into auto-filling credentials for the currently active website instead of the website that actually triggered the dialog, potentially leading to credential theft.
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
< 89.0CVSS 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
- None
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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 for Android versionOpen Firefox for Android, tap the three-dot menu, go to Settings, scroll to the bottom and tap 'About Firefox' to see the version numberAffected if Version is less than 89.0
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Confirm it is Firefox for AndroidVerify the installed application is Mozilla Firefox for Android (not Firefox Focus, Firefox Preview, or desktop Firefox)Affected if The vulnerable application is Firefox for Android specifically
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Check if password manager is enabledIn Firefox for Android Settings, go to 'Logins and passwords' or 'Privacy' and verify if 'Ask to save logins and passwords' or the built-in password manager is turned onAffected if Password manager is enabled and stores saved credentials
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Check for saved login credentialsIn Firefox for Android Settings, go to 'Logins and passwords' > 'Saved logins' to see if any website credentials are storedAffected if There are saved credentials that could be auto-filled and spoofed
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Check for active browsing sessionsDetermine if the user typically keeps multiple tabs open or has active sessions on websites while browsing, which would be required for the attack to workAffected if User maintains active website sessions while browsing other sites
The environment is affected if Firefox for Android version is below 89.0, the built-in password manager is enabled, and the user has saved credentials that could be auto-filled.
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.
From vendor data89.0
Upgrade Firefox for Android to version 89 or later to address this password manager credential spoofing vulnerability.
Fix this in Firefox
Scoped from the published advisory
- Consultation1.0 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 $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-29965 — 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-2021-29965 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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- 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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