CVE-2016-5253 in Firefox
Summary
by MITRE
The Updater in Mozilla Firefox before 48.0 on Windows allows local users to write to arbitrary files via vectors involving the callback application-path parameter and a hard link.
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Analysis
by VulDB Data Team • 03/16/2019
The vulnerability identified as CVE-2016-5253 represents a significant local privilege escalation risk within Mozilla Firefox versions prior to 48.0 on Windows operating systems. This flaw exists within the browser's updater component and exploits a critical weakness in how the application handles file path resolution during update operations. The vulnerability specifically targets the callback application-path parameter mechanism, which is designed to facilitate automated updates but becomes exploitable when combined with malicious hard link creation techniques.
The technical exploitation of this vulnerability relies on the improper handling of file paths in the Windows environment where Firefox attempts to write update files. When the updater processes a callback application-path parameter, it fails to properly validate or sanitize the target file path, allowing an attacker to manipulate the update process through hard link manipulation. This creates a race condition scenario where an attacker can establish a hard link to a target file that the updater intends to modify, effectively redirecting the update process to write arbitrary content to locations that would normally be protected or restricted. The flaw stems from insufficient path validation and lacks proper access control mechanisms when processing update callbacks.
The operational impact of CVE-2016-5253 extends beyond simple local privilege escalation to potentially enable full system compromise when combined with other attack vectors. An attacker with low-privilege access can leverage this vulnerability to write malicious code to system-critical files, potentially including registry entries, system executables, or configuration files. This vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, and represents a classic example of a path traversal attack that has been prevalent in Windows applications. The attack requires local system access but can be particularly dangerous in environments where users may have varying privilege levels or where automated update mechanisms are enabled.
Security professionals should note that this vulnerability demonstrates the importance of proper input validation and path handling in update mechanisms. The flaw violates fundamental security principles by not implementing adequate access controls or path sanitization during critical update operations. Organizations should prioritize immediate patching of affected Firefox installations to prevent exploitation, as the vulnerability can be exploited without user interaction once local access is obtained. The remediation strategy should include not only updating to Firefox 48.0 or later but also implementing monitoring for suspicious file write operations and hard link creation patterns that may indicate exploitation attempts. This vulnerability also highlights the need for comprehensive security testing of update mechanisms, particularly those involving file system operations and privilege escalation paths, as outlined in the ATT&CK framework's privilege escalation techniques.