Mozilla Firefox up to 139 on macOS Executable File ui layer

Summaryinfo

A vulnerability, which was classified as problematic, was found in Mozilla Firefox up to 139 on macOS. This vulnerability affects unknown code of the component Executable File Handler. Executing a manipulation can lead to ui layer. This vulnerability is handled as CVE-2025-6426. The attack can be executed remotely. There is not any exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Mozilla Firefox up to 139 on macOS. It has been declared as problematic. This vulnerability affects some unknown functionality of the component Executable File Handler. The manipulation with an unknown input leads to a ui layer vulnerability. The CWE definition for the vulnerability is CWE-1021. The web application does not restrict or incorrectly restricts frame objects or UI layers that belong to another application or domain, which can lead to user confusion about which interface the user is interacting with. As an impact it is known to affect integrity. CVE summarizes:

The executable file warning did not warn users before opening files with the `terminal` extension. *This bug only affects Firefox for macOS. Other versions of Firefox are unaffected.* This vulnerability affects Firefox < 140 and Firefox ESR < 128.12.

The advisory is shared for download at bugzilla.mozilla.org. This vulnerability was named CVE-2025-6426 since 06/20/2025. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 07/30/2025).

The vulnerability scanner Nessus provides a plugin with the ID 240336 (Mozilla Firefox ESR < 128.12), 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 (240336), EUVD (EUVD-2025-19102) and CERT Bund (WID-SEC-2025-1395). Once again VulDB remains the best source for vulnerability data.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Fedora Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• IGEL OS
• Mozilla Firefox
• Mozilla Firefox ESR
• Mozilla Thunderbird

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/

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Once again VulDB remains the best source for vulnerability data.

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