dbcve.org
FirefoxWeb browser · Mozilla

CVE-2021-43544

MEDIUM · 6.1 CVSS v3.1 Published 2021-12-08
Fix available
A fix is available. Upgrade to 95.0 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

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
When receiving a URL through a SEND intent, Firefox would have searched for the text, but subsequent usages of the address bar might have caused the URL to load unintentionally, which could lead to XSS and spoofing attacks. *This bug only affects Firefox for Android. Other operating systems are unaffected.*. This vulnerability affects 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 confidence

When Firefox for Android receives a URL via SEND intent, it searches for the text instead of immediately loading the URL. However, subsequent interactions with the address bar cause the URL to load automatically, potentially executing malicious scripts (XSS) or displaying deceptive URLs (spoofing). This is a logic flaw in intent handling that allows unintended script execution.

MitigationUpdate Firefox for Android to version 95 or later. Users should also be cautious when receiving URLs via SEND intents from untrusted sources.

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:< 95.0

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
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Firefox for Android installation
    Check if Firefox for Android is installed on the device by viewing installed applications in Settings > Apps, or use ADB command: `adb shell pm list packages | grep firefox`
    Affected if Firefox for Android package (org.mozilla.firefox) is found on the device
  2. Determine Firefox for Android version
    Navigate to Settings > Apps > Firefox > App info, or use ADB: `adb shell dumpsys package org.mozilla.firefox | grep versionName`
    Affected if A version number is displayed for Firefox for Android
  3. Compare version to affected range
    Compare the installed version number to the affected range: versions prior to 95.0 are vulnerable
    Affected if The installed version is below 95.0 (e.g., 94.0, 93.0, etc.)

If Firefox for Android is installed and the version is below 95.0, the device is affected by this CVE and may execute malicious scripts or display deceptive URLs when receiving URLs via SEND intents.

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 95.0 or later
Fixed in 95.0
Interim mitigation

Update Firefox for Android to version 95 or later. Users should also be cautious when receiving URLs via SEND intents from untrusted sources.

Recommended fix High confidence

Firefox 95.0 for Android

  1. 1. Open the Google Play Store app on your Android device
  2. 2. Search for 'Firefox' or 'Mozilla Firefox'
  3. 3. Tap on the Firefox app listing
  4. 4. If an update is available, tap the 'Update' button
  5. 5. Wait for the update to download and install
  6. 6. Alternatively, enable auto-updates for Firefox in the Play Store app settings to ensure future security updates are applied automatically
  7. 7. After updating, verify the version by opening Firefox, tapping the three-dot menu, selecting 'Settings', and checking the version number (should be 95.0 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
  • Testing1.0 h
  • Review / QA1.0 h
3.0 hours of engineering $750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.

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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-2021-43544 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