---
id: CVE-2025-6431
title: >-
  When a link can be opened in an external application, Firefox for Android
  will, by default, prompt the user before doing so
summary: >-
  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 privac…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N'
cwe:
  - CWE-285
vendor: mozilla
product: firefox
affected:
  - firefox < 140.0
patched:
  - firefox 140.0
published: '2025-06-24'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T18:10:00.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-6431'
references:
  - url: 'https://bugzilla.mozilla.org/show_bug.cgi?id=1942716'
    label: security@mozilla.org
  - url: 'https://www.mozilla.org/security/advisories/mfsa2025-51/'
    label: security@mozilla.org
tags:
  - nvd
epss: 0.00251
epssPercentile: 0.14866
ingestedAt: '2026-09-30T18:17:24.444Z'
---

## Overview

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.

## Affected

- `firefox < 140.0`

## Remediation

Upgrade past the affected range:

- `firefox 140.0`