CVE-2003-0171 in Mac OS X
Summary
by MITRE
DirectoryServices in MacOS X trusts the PATH environment variable to locate and execute the touch command, which allows local users to execute arbitrary commands by modifying the PATH to point to a directory containing a malicious touch program.
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Analysis
by VulDB Data Team • 12/24/2024
The vulnerability identified as CVE-2003-0171 represents a classic path manipulation flaw that existed within the DirectoryServices component of MacOS X operating systems. This issue stems from the improper handling of environment variables, specifically the PATH variable, which is fundamental to how operating systems locate executable programs. The vulnerability is particularly concerning because it demonstrates how a seemingly innocuous environment variable can be exploited to gain unauthorized command execution privileges within a system. The flaw resides in the trust model that MacOS X implemented for the PATH environment variable, where the system automatically uses the first instance of an executable found in the PATH search order without sufficient validation of the source or integrity of the executable.
The technical exploitation of this vulnerability occurs when a local attacker modifies the PATH environment variable to prioritize a maliciously crafted touch command located in a directory they control. The touch command is commonly used for setting file timestamps and is typically available in standard Unix-like systems. When DirectoryServices attempts to execute touch as part of its normal operations, it inadvertently executes the attacker-controlled malicious version instead of the legitimate system touch command. This creates a privilege escalation scenario where arbitrary code can be executed with the privileges of the DirectoryServices process, which typically runs with elevated permissions. The vulnerability is classified under CWE-426 as an Untrusted Search Path, which is a well-documented weakness in software design that allows attackers to manipulate the execution flow of programs by controlling the search path used to locate executables.
From an operational impact perspective, this vulnerability poses significant risks to MacOS X systems as it provides local attackers with a method to execute arbitrary commands without requiring remote access or complex exploitation techniques. The attack vector is relatively simple and can be executed by any user with local access to the system, making it particularly dangerous in multi-user environments where system integrity is paramount. The implications extend beyond simple command execution, as the DirectoryServices process often operates with elevated privileges and may have access to sensitive system resources, potentially enabling attackers to escalate their privileges further or access protected data. This vulnerability demonstrates how improper environment variable handling can create persistent security weaknesses that may be difficult to detect and remediate.
The mitigation strategies for CVE-2003-0171 focus on addressing the root cause of the vulnerability through proper environment variable handling and execution path validation. System administrators should implement strict PATH validation procedures that ensure executables are located in trusted directories and that the search path does not include untrusted locations. The recommended approach involves configuring applications to use absolute paths for executable commands rather than relying on PATH resolution, which aligns with the principle of least privilege and secure coding practices. Additionally, system hardening measures should include monitoring for unauthorized PATH modifications and implementing access controls that prevent local users from modifying critical system environment variables. This vulnerability highlights the importance of following secure coding guidelines and adheres to the ATT&CK framework's concept of privilege escalation through environment variable manipulation, where attackers exploit weak trust models to gain elevated system privileges. Organizations should also consider implementing runtime protections and monitoring solutions that can detect suspicious PATH modifications and unauthorized command executions to provide defense-in-depth against similar vulnerabilities.