CVE-2015-7024 in Mac OS X
Summary
by MITRE
Untrusted search path vulnerability in Apple OS X before 10.11.1 allows local users to bypass intended Gatekeeper restrictions and gain privileges via a Trojan horse program that is loaded from an unexpected directory by an application that has a valid Apple digital signature.
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Analysis
by VulDB Data Team • 07/05/2018
The vulnerability identified as CVE-2015-7024 represents a critical untrusted search path issue affecting Apple macOS versions prior to 10.11.1. This flaw exploits the operating system's trust model by allowing malicious actors to bypass Gatekeeper security mechanisms through carefully crafted Trojan horse programs. The vulnerability specifically targets applications that possess legitimate Apple digital signatures, which normally grant them trusted status within the system's security framework. Attackers can leverage this weakness to execute arbitrary code with elevated privileges by placing malicious binaries in directories that are searched before the intended locations, effectively subverting the system's intended security controls.
The technical implementation of this vulnerability stems from improper handling of library search paths within macOS applications that have valid Apple code signatures. When applications execute, they follow a predetermined search order to locate required libraries and executables, but the system fails to properly validate the source of these components. This behavior creates a path traversal opportunity where attackers can place malicious executables in directories that are searched before the legitimate system locations. The flaw is particularly dangerous because it operates under the assumption that any executable loaded by a signed application is trustworthy, even when loaded from unexpected or unauthorized directories.
From an operational perspective, this vulnerability enables local privilege escalation attacks that can bypass the fundamental security protections designed to prevent unauthorized code execution. The impact extends beyond simple code execution as it allows attackers to circumvent Gatekeeper's intended protection mechanisms, which are specifically designed to prevent the execution of unsigned or malicious software. This weakness essentially undermines the entire code signing architecture that macOS employs to maintain system integrity, as it allows attackers to exploit the trust relationship between signed applications and the operating system. The vulnerability is particularly concerning because it requires no network connectivity or remote exploitation, making it a purely local attack vector that can be executed by any user with access to the affected system.
The attack surface for this vulnerability is significant as it affects any macOS application that loads libraries from potentially untrusted locations, particularly those with valid Apple code signatures. Security professionals should note that this vulnerability aligns with CWE-427 Uncontrolled Search Path Element, which describes the dangerous practice of allowing applications to search in directories that are not properly controlled or validated. The mitigation strategies should focus on ensuring that applications properly validate library paths and implement secure coding practices that prevent the loading of executables from unexpected directories. Additionally, this vulnerability demonstrates the importance of proper privilege separation and the principle of least privilege in system design, as it allows attackers to escalate their privileges through seemingly legitimate application execution paths. Organizations should implement comprehensive patch management procedures to ensure that macOS systems are updated to versions that address this vulnerability, as the flaw represents a fundamental weakness in the system's security architecture that could be exploited by sophisticated attackers.
This vulnerability also relates to several ATT&CK tactics including privilege escalation and defense evasion, as attackers can use it to bypass security controls and execute malicious code with elevated privileges. The attack pattern follows the typical methodology of leveraging trusted applications to execute malicious payloads, which is a common technique in advanced persistent threat campaigns. The remediation approach should include both immediate patching of affected systems and implementation of additional monitoring controls to detect suspicious library loading behaviors, as the vulnerability can be difficult to detect through traditional security measures due to its reliance on legitimate code signing practices.