CVE-2016-4640 in Mac OS X
Summary
by MITRE
Login Window in Apple OS X before 10.11.6 allows attackers to execute arbitrary code in a privileged context, obtain sensitive user information, or cause a denial of service (memory corruption) via a crafted app.
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Analysis
by VulDB Data Team • 09/30/2024
The vulnerability identified as CVE-2016-4640 resides within the Login Window component of Apple's macOS operating system, affecting versions prior to 10.11.6. This critical flaw exists in the privileged execution context of the system's authentication framework, specifically within the login window process that handles user authentication and system access control. The vulnerability represents a significant security weakness that undermines the fundamental integrity of the operating system's authentication mechanisms.
The technical implementation of this vulnerability stems from improper input validation and memory handling within the Login Window's processing pipeline. Attackers can exploit this weakness by crafting a malicious application that, when executed, triggers a memory corruption vulnerability during the authentication process. This memory corruption occurs when the system attempts to process the crafted application's metadata or resources within the privileged context of the login window. The flaw operates under CWE-125, which describes out-of-bounds read conditions, and potentially CWE-787, representing out-of-bounds write vulnerabilities, both of which enable attackers to manipulate memory structures that should remain protected.
The operational impact of this vulnerability extends across multiple attack vectors and security implications. An attacker who successfully exploits this vulnerability can execute arbitrary code with elevated privileges, effectively bypassing the standard user authentication mechanisms. This privilege escalation allows malicious actors to access sensitive user information, including passwords, personal data, and system credentials that are typically protected by the operating system's security model. Additionally, the memory corruption aspect can be leveraged to cause denial of service conditions, potentially crashing the login window process or even the entire operating system, leading to system instability and potential data loss.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation,' and T1547.001, covering 'Registry Run Keys / Startup Folder' exploitation methods. The attack surface is particularly concerning because it operates at the system level during the authentication phase, meaning that any user interaction with the login window could potentially trigger the exploit. This makes the vulnerability particularly dangerous in environments where users might encounter malicious applications through social engineering or other attack vectors, as the exploitation requires minimal user interaction beyond normal system usage.
The mitigation strategies for CVE-2016-4640 primarily focus on immediate system updates and security hardening measures. Apple's official patch for this vulnerability requires users to upgrade to macOS 10.11.6 or later, which includes enhanced input validation and memory safety improvements within the Login Window component. Organizations should implement comprehensive patch management protocols to ensure all systems receive the necessary updates promptly. Additional security measures include monitoring for suspicious application execution patterns, implementing application whitelisting policies, and conducting regular security assessments of system authentication components. Network administrators should also consider deploying intrusion detection systems to monitor for potential exploitation attempts targeting this specific vulnerability, as the memory corruption behavior may generate detectable network traffic patterns or system call sequences that can be monitored through security information and event management systems.