CVE-2025-6426 in Firefox
Summary
by MITRE • 06/24/2025
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.
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Analysis
by VulDB Data Team • 07/30/2025
The vulnerability described in CVE-2025-6426 represents a critical user interface security flaw within Firefox's file handling mechanisms on macOS systems. This issue specifically targets the executable file warning system that should normally alert users before opening potentially dangerous file types. The flaw manifests when Firefox encounters files with the terminal extension, failing to present the expected warning dialogue that would typically inform users about the potential risks associated with executing code. This represents a significant bypass of the browser's security model that is designed to protect users from inadvertently running malicious executables.
The technical nature of this vulnerability stems from an incomplete implementation of Firefox's file type validation system. When Firefox processes files with the terminal extension on macOS, the browser fails to invoke its standard warning mechanism that would normally prompt users with a dialog box containing security warnings about executing potentially harmful code. This failure occurs specifically within the macOS implementation of Firefox, indicating a platform-specific code path that was not properly updated or tested against the security requirements for executable file handling. The vulnerability creates a direct path for malicious actors to potentially deliver and execute code without user awareness or consent, fundamentally undermining the browser's security assurances.
The operational impact of this vulnerability is particularly severe given that it affects a widely used web browser on a platform where users expect robust security protections. Attackers could exploit this vulnerability by crafting malicious websites that deliver files with terminal extensions, potentially leading to unauthorized code execution on targeted systems. The vulnerability affects Firefox versions prior to 140 and Firefox ESR versions prior to 128.12, representing a substantial user base that would remain exposed to this threat. This flaw directly violates the principle of least privilege and user consent that forms the foundation of secure software design, as users are not properly informed about the potential risks when interacting with executable content.
Security professionals should note that this vulnerability aligns with CWE-693, which addresses protection mechanism failures, and represents a clear violation of the principle that security warnings should be presented before potentially dangerous actions are executed. The ATT&CK framework categorizes this issue under T1059.007 for Command and Scripting Interpreter: JavaScript and potentially T1566 for Phishing, as it enables more sophisticated social engineering attacks by removing the user's ability to make informed decisions about executing potentially malicious code. Organizations should immediately implement patch management procedures to update Firefox installations to versions 140 or later for regular releases and 128.12 or later for ESR releases, while also considering temporary network-level mitigations such as content filtering to prevent access to potentially malicious sites until full patch deployment occurs. The vulnerability demonstrates the critical importance of comprehensive testing across all supported platforms and the necessity of maintaining consistent security warning mechanisms regardless of file type or extension.