CVE-2016-7255 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, Windows 10 Gold, 1511, and 1607, and Windows Server 2016 allow local users to gain privileges via a crafted application, aka "Win32k Elevation of Privilege Vulnerability."
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Analysis
by VulDB Data Team • 09/09/2024
The CVE-2016-7255 vulnerability represents a critical privilege escalation flaw within the Windows kernel-mode drivers, specifically affecting the win32k.sys component that manages user interface elements and graphics rendering. This vulnerability exists in multiple Windows versions including 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, Windows 10 versions 1511 and 1607, and Windows Server 2016. The flaw stems from improper validation of user-mode input within kernel-level code, creating a dangerous condition where malicious applications can manipulate kernel memory structures to execute arbitrary code with system-level privileges.
The technical implementation of this vulnerability involves a use-after-free condition in the win32k.sys driver that handles graphics object management and windowing operations. When a malicious application creates and manipulates graphics objects in a specific sequence, it can cause the kernel to free memory that is subsequently accessed by another thread, leading to memory corruption. This memory corruption can be exploited to overwrite critical kernel data structures or function pointers, ultimately allowing attackers to execute code with kernel privileges. The vulnerability specifically affects the handling of GDI (Graphics Device Interface) objects during window creation and manipulation operations, making it particularly dangerous in environments where users can run untrusted applications.
The operational impact of CVE-2016-7255 is severe and far-reaching, as it enables local attackers to achieve privilege escalation from standard user level to SYSTEM level without requiring additional attack vectors. This means that any user with access to a vulnerable system can potentially gain complete control over the machine, allowing for data exfiltration, persistence establishment, and further network reconnaissance. The vulnerability is particularly concerning because it requires no user interaction beyond running a malicious application, making it ideal for automated exploitation in targeted attacks. Security researchers have noted that this vulnerability can be leveraged in conjunction with other attack techniques to create persistent backdoors, as demonstrated by various threat actors who have incorporated it into their exploit toolkits.
Mitigation strategies for CVE-2016-7255 primarily focus on applying Microsoft's security patches released in August 2016 as part of the security bulletin MS16-111. Organizations should prioritize immediate deployment of the relevant updates across all affected Windows systems, particularly those running older versions such as Windows Vista and Server 2008. Additional defensive measures include implementing application whitelisting policies to prevent execution of untrusted code, disabling unnecessary graphics features that might trigger the vulnerability, and monitoring for suspicious process behavior related to win32k.sys operations. The vulnerability aligns with CWE-476 which describes null pointer dereference conditions, and maps to ATT&CK technique T1068 which covers local privilege escalation through kernel exploits. Network administrators should also consider implementing monitoring solutions that can detect anomalous kernel-mode memory access patterns and unusual graphics driver behavior that might indicate exploitation attempts.