CVE-2015-2720 in Firefox
Summary
by MITRE
The update implementation in Mozilla Firefox before 38.0 on Windows does not ensure that the pathname for updater.exe corresponds to the application directory, which might allow local users to gain privileges via a Trojan horse file.
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Analysis
by VulDB Data Team • 05/17/2022
The vulnerability identified as CVE-2015-2720 resides within the update mechanism of Mozilla Firefox versions prior to 38.0 on Windows operating systems. This flaw represents a critical security weakness that stems from inadequate validation of file paths during the software update process. The issue specifically affects how Firefox handles the execution of updater.exe, a component responsible for managing automatic updates to the browser. When Firefox attempts to update itself, it must execute this updater utility to perform the necessary modifications to the application files.
The technical root cause of this vulnerability lies in the improper path validation logic within Firefox's update implementation. The software fails to verify that the pathname of updater.exe matches the expected application directory, creating an opportunity for malicious actors to exploit this weakness. This validation failure occurs because the application does not perform a comprehensive check to ensure that the updater executable originates from the legitimate application directory rather than a potentially compromised location. The vulnerability is particularly concerning because it operates at the privilege level of the user running Firefox, allowing local attackers to manipulate the update process through a Trojan horse file attack vector.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the integrity of Firefox's update mechanism. Local users who can place malicious files in strategic locations on the system can potentially execute arbitrary code with elevated privileges when Firefox attempts to update itself. This attack vector is particularly dangerous because it leverages the legitimate update process, making it more difficult to detect and prevent. The vulnerability creates a persistent security risk that could be exploited by malware authors or attackers who gain access to a user's system, allowing them to install malicious updates that would otherwise be blocked by the browser's security model.
This vulnerability maps directly to CWE-78, which addresses the execution of system commands, and aligns with ATT&CK technique T1059.001 for command and scripting interpreter. The flaw enables adversaries to execute code through the legitimate update process, bypassing typical security controls that would normally prevent unauthorized modifications to system components. Organizations should consider this vulnerability as part of a broader attack surface that includes privilege escalation vectors and file system manipulation techniques. The security implications suggest that systems running affected versions of Firefox should be prioritized for immediate patching, as the vulnerability could be exploited by attackers without requiring any special privileges beyond local access to the system. Mitigation strategies should focus on updating to Firefox 38.0 or later versions where the path validation has been properly implemented, along with network monitoring to detect unusual update activity that might indicate exploitation attempts.