CVE-2015-3709 in Mac OS X
Summary
by MITRE
Race condition in kext tools in Apple OS X before 10.10.4 allows local users to bypass intended signature requirements for kernel extensions by leveraging improper pathname validation.
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Analysis
by VulDB Data Team • 11/25/2024
The vulnerability described in CVE-2015-3709 represents a critical race condition affecting kernel extension tools within Apple's macOS operating system prior to version 10.10.4. This flaw resides in the kext tools component that manages kernel extension signatures and validation processes, creating a security mechanism that can be exploited by local attackers to circumvent intended security controls. The race condition occurs during the validation process of kernel extension signatures, where improper pathname validation allows malicious actors to manipulate the system's trust mechanisms. This vulnerability specifically impacts the kernel extension loading process and undermines the operating system's core security model that relies on signed kernel extensions to prevent unauthorized code execution at kernel level.
The technical implementation of this vulnerability stems from a timing issue in how kext tools handle pathname validation during kernel extension signature verification. When a kernel extension is loaded, the system performs signature checks that should prevent unsigned or improperly signed extensions from executing. However, due to the race condition, an attacker can exploit a window of opportunity where the system validates a temporary or intermediate pathname rather than the final intended location of the kernel extension. This allows attackers to substitute a malicious extension for a legitimate one during the validation process, effectively bypassing the signature requirements that should prevent such unauthorized code execution. The flaw operates at the intersection of filesystem operations and kernel security controls, making it particularly dangerous as it can be leveraged to load malicious kernel code that would normally be blocked by the system's security mechanisms.
The operational impact of CVE-2015-3709 is significant as it provides local attackers with a means to escalate privileges and execute arbitrary code at kernel level without proper authentication or signature validation. This vulnerability can be exploited by any local user with access to the system, making it particularly concerning for multi-user environments or systems where privilege separation is critical. Attackers can leverage this flaw to load malicious kernel extensions that can modify system behavior, monitor user activities, or establish persistent backdoors. The vulnerability essentially undermines the fundamental security model of macOS kernel extension management, where the system should enforce strict signature validation before any kernel code can execute. This creates opportunities for attackers to bypass security controls that are designed to prevent unauthorized kernel code execution, potentially leading to full system compromise and persistent access to affected systems.
The mitigation strategies for this vulnerability involve updating to Apple macOS version 10.10.4 or later, which includes fixes for the race condition in kext tools and proper pathname validation. System administrators should also implement monitoring for unusual kernel extension loading activities and ensure that only trusted kernel extensions are loaded on systems. Additional security measures include enabling System Integrity Protection where available, restricting local user privileges, and maintaining regular system updates to address similar vulnerabilities. This vulnerability aligns with CWE-367, which describes a time-of-check to time-of-use race condition, and represents a classic example of how improper synchronization in security-critical operations can lead to privilege escalation. From an ATT&CK perspective, this vulnerability maps to privilege escalation techniques and can be used to establish persistence through kernel-level modifications, making it a significant concern for security operations centers monitoring for advanced persistent threats.