CVE-2015-4505 in Firefox
Summary
by MITRE
updater.exe in Mozilla Firefox before 41.0 and Firefox ESR 38.x before 38.3 on Windows allows local users to write to arbitrary files by conducting a junction attack and waiting for an update operation by the Mozilla Maintenance Service.
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Analysis
by VulDB Data Team • 10/22/2024
The vulnerability identified as CVE-2015-4505 represents a critical file system privilege escalation flaw within Mozilla Firefox's update mechanism on Windows operating systems. This vulnerability specifically affects Firefox versions prior to 41.0 and Firefox ESR 38.x versions prior to 38.3, creating a significant security risk for Windows users who rely on these browser versions. The flaw exploits a fundamental weakness in how the Mozilla Maintenance Service handles file operations during the update process, allowing malicious actors to manipulate the system's file structure through a sophisticated junction attack technique.
The technical implementation of this vulnerability leverages Windows file system junction points to redirect file operations to arbitrary locations. When Firefox performs its update routine, the Mozilla Maintenance Service attempts to write to specific files within the Firefox installation directory. An attacker who has local access to the system can create a junction point that appears to be a legitimate update file but actually points to a location outside the intended directory structure. This junction attack allows the attacker to manipulate the update process and write malicious content to files that would normally be protected from modification by regular users. The vulnerability stems from insufficient input validation and path resolution within the update service, creating a path traversal scenario that violates standard security boundaries.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with the ability to modify critical browser components and potentially gain persistent access to affected systems. Once an attacker successfully executes this junction attack, they can overwrite essential Firefox files with malicious payloads, modify browser configuration settings, or establish backdoors within the browser environment. The attack requires local system access but does not necessitate elevated privileges initially, making it particularly dangerous in environments where users have standard accounts but may be targeted through social engineering or other initial compromise techniques. This vulnerability directly relates to CWE-22, which describes improper limitation of a pathname to a restricted directory, and aligns with ATT&CK technique T1059.001 for execution through Windows Command Shell, as the attack can be extended to execute arbitrary code through modified browser components.
Mitigation strategies for this vulnerability primarily focus on immediate patching of affected Firefox installations to versions 41.0 or later for standard releases and 38.3 or later for ESR releases. System administrators should prioritize updating all affected systems and implement monitoring for suspicious file system activities around Firefox installation directories. Additional protective measures include restricting local user access to system directories where Firefox updates occur, implementing file system permissions that prevent unauthorized junction point creation, and deploying endpoint protection solutions that can detect and block suspicious update-related file operations. Organizations should also consider implementing application whitelisting policies to control which processes can modify Firefox installation files, and establish regular security audits to identify potential junction point vulnerabilities in system configurations. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date software and implementing proper file system security controls to prevent privilege escalation attacks that exploit update mechanisms.