CVE-2016-3266 in Windows
Summary
by MITRE
The kernel-mode drivers in Microsoft Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, and Windows 10 Gold, 1511, and 1607 allow local users to gain privileges via a crafted application, aka "Win32k Elevation of Privilege Vulnerability," a different vulnerability than CVE-2016-3376, CVE-2016-7185, and CVE-2016-7211.
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Analysis
by VulDB Data Team • 09/23/2022
The Win32k Elevation of Privilege Vulnerability represents a critical security flaw in Microsoft Windows kernel-mode drivers that affects multiple operating system versions including Windows Vista SP2 through Windows 10 1607. This vulnerability resides within the win32k.sys driver which manages user-mode graphics components and handles windowing system operations. The flaw enables local attackers with standard user privileges to execute arbitrary code with kernel-level privileges, effectively bypassing the operating system's security model and allowing full system compromise. The vulnerability specifically impacts the graphics subsystem's handling of user-mode display drivers and window management functions, making it particularly dangerous as it leverages legitimate system components to escalate privileges. According to CWE-269, this vulnerability falls under inadequate privilege management, where the kernel-mode component fails to properly validate input from user-mode applications, creating a path for privilege escalation attacks.
The technical implementation of this vulnerability occurs through improper validation of graphics-related data structures within the win32k.sys driver. Attackers can craft malicious applications that exploit memory corruption issues when processing graphics operations, particularly those involving window management and display driver interfaces. The flaw allows for arbitrary code execution in kernel context, which means that any user-level process can potentially elevate its privileges to system level. This type of vulnerability typically involves use-after-free conditions or buffer overflows that occur when the kernel driver handles malformed graphics data from user applications. The ATT&CK framework categorizes this under privilege escalation techniques, specifically targeting the 'Exploitation for Privilege Escalation' tactic where adversaries leverage software vulnerabilities to gain elevated system access. The vulnerability's exploitation requires local system access but does not need network connectivity, making it particularly concerning for environments where user accounts may be compromised through social engineering or other attack vectors.
The operational impact of CVE-2016-3266 is severe and far-reaching across enterprise environments, as it allows attackers to establish persistent system-level access without requiring network-based attack vectors. Once exploited, the vulnerability provides complete control over affected systems, enabling data exfiltration, lateral movement, and establishment of backdoors. Organizations running affected Windows versions face significant risk of full system compromise, as the vulnerability can be exploited through seemingly legitimate user applications or malicious software installed by attackers. The impact extends beyond individual systems to potentially affect entire networks, especially in environments where users have standard privileges and where privilege escalation attacks can be used to gain access to domain controller systems. This vulnerability is particularly dangerous in corporate environments where user accounts may be compromised through phishing attacks, and where the attacker can leverage the privilege escalation to move laterally through the network infrastructure.
Microsoft released security patches for this vulnerability through their regular update cycle, but many organizations remained vulnerable for extended periods due to delayed patch deployment or system maintenance windows. The recommended mitigations include immediate installation of the applicable security updates from Microsoft's security bulletin, implementing the principle of least privilege by limiting user account privileges, and monitoring for suspicious system behavior that might indicate exploitation attempts. Security administrators should also consider implementing application whitelisting policies to prevent execution of unauthorized applications that might exploit this vulnerability. Additionally, network segmentation and monitoring solutions should be deployed to detect potential exploitation attempts, particularly around graphics-related system calls and user-mode to kernel-mode transitions. The vulnerability demonstrates the importance of maintaining up-to-date security patches and highlights the critical nature of kernel-mode vulnerabilities that can be exploited by local attackers to achieve system compromise. Organizations should conduct regular vulnerability assessments to identify systems running affected Windows versions and ensure timely patch deployment to protect against this and similar privilege escalation vulnerabilities.