Mozilla Firefox up to 139 on Android Link improper authorization

Summaryinfo

A vulnerability marked as problematic has been reported in Mozilla Firefox up to 139 on Android. Affected by this issue is some unknown functionality of the component Link Handler. This manipulation causes an unknown weakness. This vulnerability is registered as CVE-2025-6431. Remote exploitation of the attack is possible. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Mozilla Firefox up to 139 on Android. It has been declared as problematic. Affected by this vulnerability is an unknown code of the component Link Handler. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect integrity. The summary by CVE is:

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 affects Firefox < 140.

The advisory is shared at bugzilla.mozilla.org. This vulnerability is known as CVE-2025-6431 since 06/20/2025. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 08/17/2025). MITRE ATT&CK project uses the attack technique T1548.002 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 242306 (SUSE SLES12 Security Update : MozillaFirefox, MozillaFirefox-branding-SLE (SUSE-SU-2025:02339-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 140 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (242306), EUVD (EUVD-2025-19087) and CERT Bund (WID-SEC-2025-1850). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

• Xerox FreeFlow Print Server

Productinfo

Type

• Web Browser

Vendor

• Mozilla

Name

• Firefox

Version

• 139

License

• open-source

Website

• Vendor: https://www.mozilla.org/
• Product: https://www.mozilla.org/en-US/firefox/

CPE 2.3info

• 🔍

CPE 2.2info

• 🔍

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Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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