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FirefoxWeb browser · Mozilla

CVE-2025-6431

MEDIUM · 6.5 CVSS v3.1 Published 2025-06-24
Fix available
A fix is available. Upgrade to 140.0 or later.
See remediation →
72/100
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 a link can be opened in an external application, Firefox for Android will, by default, prompt the user before doing so. An attacker could have bypassed this prompt, potentially exposing the user to security vulnerabilities or privacy leaks in external applications. *This bug only affects Firefox for Android. Other versions of Firefox are unaffected.*. This vulnerability was fixed in Firefox 140.

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

Firefox for Android includes a security prompt that asks users before opening links in external applications. This vulnerability allowed attackers to bypass that prompt, automatically launching external applications without user consent. This could lead to exploitation of vulnerabilities or privacy leaks in those external applications.

MitigationEnsure all Firefox for Android installations are updated to version 140 or later. Implement mobile device management policies to enforce automatic app updates.

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:< 140.0

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
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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 if Firefox for Android is installed
    Check device for Mozilla Firefox app - via Settings > Apps, or by attempting to query the package via ADB: 'adb shell pm list packages | grep mozilla'
    Affected if The package 'org.mozilla.firefox', 'org.mozilla.fennec_fdroid', or similar Mozilla Firefox package is present on the device
  2. Check the installed Firefox for Android version
    Via Settings > Apps > Firefox > App info, or via ADB: 'adb shell dumpsys package org.mozilla.firefox | grep versionName'
    Affected if The reported version is earlier than 140.0 (for example 139.x, 138.x, etc.)
  3. Verify if the external app link prompt is configured
    In Firefox for Android, navigate to Settings > Links > Open external apps (or similar path depending on version). Check if 'Ask before opening' or similar prompt option exists and is enabled.
    Affected if The security prompt asking before opening links in external applications is disabled, missing, or can be bypassed (indicating the vulnerable configuration)

A user is affected if Firefox for Android version 139.x or earlier is installed on their device, with the external app launch prompt configured in a way that allows bypass.

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 140.0 or later
Fixed in 140.0
Interim mitigation

Ensure all Firefox for Android installations are updated to version 140 or later. Implement mobile device management policies to enforce automatic app updates.

Recommended fix High confidence

Firefox 140.0 (Android)

  1. Open the Google Play Store app on your Android device
  2. Search for 'Firefox' or 'Mozilla Firefox'
  3. Locate the Firefox app in the search results
  4. Tap on the Firefox app to open its page
  5. If an update is available, tap the 'Update' button; otherwise, ensure you have version 140.0 or later
  6. Wait for the update to download and install
  7. Once installed, verify the version by going to Firefox > Settings > About Firefox, which should show version 140.0 or higher
Caveat Minimal risk; this is a security patch upgrade that does not introduce breaking changes for typical users

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Firefox Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

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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-2025-6431 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