CVE-2016-7300 in Office
Summary
by MITRE
Untrusted search path vulnerability in Microsoft Auto Updater for Mac allows local users to gain privileges via a Trojan horse executable file, aka "Microsoft (MAU) Office Elevation of Privilege Vulnerability."
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Analysis
by VulDB Data Team • 10/08/2022
The CVE-2016-7300 vulnerability represents a critical privilege escalation flaw in Microsoft Auto Updater for Mac systems that demonstrates the dangers of insecure search path implementations in software update mechanisms. This vulnerability specifically affects Microsoft Auto Updater versions prior to 3.18.0 and exposes a fundamental design flaw where the updater process fails to properly validate executable paths during the update process. The issue stems from the application's reliance on a predictable search path that does not adequately verify the authenticity or integrity of executables located in user-accessible directories, creating an opportunity for malicious actors to exploit this weakness through carefully crafted file placement attacks.
The technical exploitation of this vulnerability occurs when a local attacker places a malicious executable file in a directory that appears earlier in the system's PATH environment variable than the legitimate Microsoft Auto Updater executable. When the updater runs and attempts to execute components from its expected search locations, it inadvertently executes the attacker-controlled binary with elevated privileges. This flaw operates under the principle of path traversal and executable hijacking, where the system's trust model is violated by the assumption that all executables in the search path are legitimate and safe. The vulnerability is classified as a privilege escalation issue that directly relates to CWE-426, which describes the insecure use of system calls that can lead to privilege escalation through executable hijacking.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable full system compromise when combined with other attack vectors. Local attackers can leverage this weakness to execute arbitrary code with elevated privileges, potentially allowing them to install persistent backdoors, modify system files, or escalate their access to administrative levels. The vulnerability is particularly concerning because it operates at the system level and can be exploited without requiring network access or user interaction, making it a stealthy and effective attack vector for adversaries seeking to establish persistent presence on Mac systems. This type of vulnerability aligns with ATT&CK technique T1068, which covers the use of privilege escalation techniques to gain higher-level access to systems.
Microsoft addressed this vulnerability through patch updates that modified the Auto Updater's search path behavior to implement proper executable validation and path resolution. The fix involved ensuring that the updater process validates the authenticity and integrity of all executables it attempts to execute, particularly by implementing proper path verification mechanisms that prevent execution of unauthorized binaries. Organizations should prioritize applying these patches immediately and implement additional security controls such as monitoring for suspicious file creation in system directories, implementing application whitelisting policies, and conducting regular security assessments of update mechanisms. The vulnerability serves as a reminder of the critical importance of secure coding practices in update systems and the need for proper input validation and path resolution in all system components that handle executable loading operations.