CVE-2016-1729 in Mac OS X
Summary
by MITRE
Untrusted search path vulnerability in OSA Scripts in Apple OS X before 10.11.3 allows attackers to load arbitrary script libraries via a quarantined application.
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Analysis
by VulDB Data Team • 07/03/2022
The vulnerability identified as CVE-2016-1729 represents a critical untrusted search path issue within Apple's OSA Scripts component of macOS operating systems prior to version 10.11.3. This flaw resides in the Open Scripting Architecture which governs how macOS handles script execution and library loading. The vulnerability specifically affects the way the system resolves script libraries when applications are launched in a quarantined state, creating a potential attack vector for privilege escalation and code execution. The issue stems from improper handling of library paths during script execution, allowing malicious actors to manipulate the library loading process through carefully crafted script files. This vulnerability operates under the broader category of CWE-427 Uncontrolled Search Path Element, which is classified as a path traversal or library loading vulnerability where the application does not properly validate or sanitize the search paths used to locate required libraries.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious script or application that, when executed in a quarantined state, causes the system to load a malicious library from an attacker-controlled location. The quarantined application environment typically restricts certain file operations and network access, but the untrusted search path flaw allows attackers to bypass these restrictions by manipulating the library resolution process. When the system attempts to load required script libraries, it follows a predetermined search order that includes user-writable directories, potentially allowing an attacker to place malicious libraries in locations that get prioritized during the loading process. This vulnerability is particularly dangerous because it leverages the legitimate quarantine mechanism that macOS employs to prevent potentially harmful applications from executing, thereby providing attackers with a legitimate execution context that can be abused to load malicious code.
The operational impact of CVE-2016-1729 extends beyond simple privilege escalation as it provides attackers with a sophisticated method for persistence and privilege elevation within macOS environments. Attackers can leverage this vulnerability to execute arbitrary code with the privileges of the quarantined application, potentially leading to complete system compromise. The vulnerability affects a wide range of applications that utilize OSA Scripts, including those that may be launched from web browsers or email clients where users might encounter quarantined applications. This creates a significant attack surface as users frequently interact with potentially malicious content from untrusted sources. The vulnerability can be exploited in various attack scenarios including phishing campaigns, drive-by downloads, and social engineering attacks where attackers can convince users to open malicious documents or applications that trigger the vulnerable code path. From an attacker's perspective, this vulnerability aligns with ATT&CK technique T1059.007 Scripting - Python, as it involves manipulating script execution environments to gain unauthorized code execution. The vulnerability also maps to T1546.003 Setuid and Setgid, as it can be used to escalate privileges through manipulated library loading. The impact is particularly severe in enterprise environments where users may encounter quarantined applications from legitimate sources, making the attack more believable and harder to detect.
Mitigation strategies for CVE-2016-1729 primarily focus on updating to Apple macOS version 10.11.3 or later, which includes the necessary patches to address the untrusted search path vulnerability. System administrators should implement comprehensive patch management policies to ensure all macOS systems are updated promptly. Additional mitigations include implementing strict application whitelisting policies that prevent execution of untrusted applications, particularly those that might leverage quarantined execution contexts. Network-level protections such as content filtering and sandboxing mechanisms can help reduce the risk of exploitation by blocking malicious content before it reaches users. Organizations should also consider implementing endpoint detection and response solutions that can monitor for suspicious library loading patterns and unauthorized script execution. The vulnerability highlights the importance of proper privilege separation and secure coding practices in macOS application development, particularly around library loading and search path resolution. Security teams should monitor for indicators of compromise related to script execution anomalies and unauthorized library loading activities. The vulnerability demonstrates the critical importance of maintaining up-to-date operating systems and following security best practices for application deployment and execution, particularly in environments where users may encounter potentially malicious content from untrusted sources. Regular security assessments should include testing for similar path traversal vulnerabilities in custom applications and scripts that may be vulnerable to similar exploitation techniques.