CVE-2016-4727 in macOS
Summary
by MITRE
IOThunderboltFamily in Apple OS X before 10.12 allows attackers to execute arbitrary code in a privileged context or cause a denial of service (memory corruption) via a crafted app.
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Analysis
by VulDB Data Team • 09/20/2022
The CVE-2016-4727 vulnerability resides within the IOThunderboltFamily component of Apple's macOS operating system, affecting versions prior to 10.12. This flaw represents a critical security issue that undermines the system's kernel security model by allowing malicious applications to escalate privileges and execute code with elevated permissions. The vulnerability specifically targets the Thunderbolt interface driver, which handles communication with Thunderbolt peripherals and manages the underlying hardware interfaces. Attackers can exploit this weakness by crafting a malicious application that leverages improper input validation within the kernel extension, bypassing normal security boundaries that should prevent user-space applications from accessing privileged system resources. The flaw demonstrates a classic privilege escalation vulnerability where unprivileged code can manipulate kernel data structures through improper bounds checking or memory handling routines.
The technical implementation of this vulnerability involves memory corruption issues within the IOThunderboltFamily kernel extension, which processes Thunderbolt device connections and manages the associated kernel memory allocations. When a crafted application attempts to interact with Thunderbolt devices through the kernel interface, it can trigger buffer overflows or use-after-free conditions that corrupt kernel memory structures. This memory corruption allows attackers to overwrite critical kernel data or execute arbitrary code within the kernel context, effectively bypassing macOS security mechanisms such as kernel address space layout randomization and code signing enforcement. The vulnerability operates at the kernel level, meaning that successful exploitation can result in complete system compromise without requiring user interaction beyond launching the malicious application. This represents a sophisticated attack vector that leverages the trust model between the operating system and hardware interfaces.
The operational impact of CVE-2016-4727 extends far beyond simple privilege escalation, as it enables attackers to gain persistent access to compromised systems while maintaining stealth. Once exploited, attackers can install rootkits, modify system binaries, or establish backdoor access that persists across reboots, making the vulnerability particularly dangerous for enterprise environments and users with elevated privileges. The memory corruption nature of the flaw also introduces potential for denial of service scenarios where system stability is compromised, leading to unexpected reboots or system crashes. The vulnerability's exploitation requires minimal user interaction, as the malicious application can be distributed through legitimate channels and executed without requiring administrator privileges initially. This makes the attack surface particularly broad, as users may unknowingly execute malicious code while performing routine computing tasks, especially when connecting Thunderbolt peripherals or running applications that interact with the Thunderbolt subsystem. The vulnerability aligns with attack patterns documented in the attack tree framework where kernel-level exploits represent the highest privilege escalation opportunities available to adversaries.
Mitigation strategies for CVE-2016-4727 primarily focus on immediate system updates and operational security measures. The most effective remediation involves upgrading to macOS 10.12 or later versions where Apple has implemented proper bounds checking and memory management within the IOThunderboltFamily component. System administrators should also implement application whitelisting policies to prevent execution of unsigned or untrusted applications, particularly those that might interact with Thunderbolt interfaces. Network segmentation and monitoring can help detect anomalous Thunderbolt device connections or unusual kernel activity that might indicate exploitation attempts. Organizations should also consider disabling Thunderbolt interfaces when not in use, as this reduces the attack surface for exploitation. The vulnerability highlights the importance of kernel security and proper input validation as outlined in the CWE-125 vulnerability category, which addresses out-of-bounds read conditions. Additionally, this vulnerability aligns with ATT&CK technique T1068 which describes privilege escalation through kernel exploits, and demonstrates the critical need for maintaining up-to-date system patches as part of comprehensive cybersecurity programs. Security teams should also implement monitoring for kernel memory corruption patterns and unusual system behavior that might indicate exploitation of similar vulnerabilities within the Thunderbolt subsystem.