CVE-2015-2527 in Windows
Summary
by MITRE
The process-initialization implementation in win32k.sys in the kernel-mode drivers in Microsoft Windows 8, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT Gold and 8.1, and Windows 10 does not properly constrain impersonation levels, which allows local users to gain privileges via a crafted application, aka "Win32k Elevation of Privilege Vulnerability."
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Analysis
by VulDB Data Team • 06/15/2025
The CVE-2015-2527 vulnerability represents a critical privilege escalation flaw within Microsoft 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 Windows 8, 8.1, Server 2012, RT, and Windows 10, making it particularly concerning for enterprise environments where these systems are prevalent. The flaw resides in how the kernel-mode driver handles process initialization and impersonation levels, creating an opportunity for local attackers to elevate their privileges from standard user level to system level access.
The technical root cause of this vulnerability stems from improper validation of impersonation levels during process initialization within the win32k.sys driver. When applications interact with the Windows kernel for graphical operations, they typically operate under specific impersonation contexts that should be strictly enforced. However, the implementation fails to properly constrain these impersonation levels, allowing malicious applications to manipulate the security context and gain unauthorized access to system resources. This represents a classic case of inadequate access control enforcement in kernel-mode code, which falls under CWE-284 Access Control vulnerabilities.
The operational impact of CVE-2015-2527 is severe as it enables local privilege escalation attacks that can be executed by any user with standard login privileges on affected systems. An attacker could craft a malicious application that exploits this vulnerability to obtain SYSTEM-level privileges without requiring administrative credentials or physical access. Once elevated, the attacker could perform actions such as modifying system files, installing malware, accessing sensitive data, or establishing persistent backdoors. The vulnerability is particularly dangerous because it operates entirely within the kernel space, making detection and prevention extremely challenging for traditional security solutions that operate at user level.
This vulnerability aligns with ATT&CK technique T1068, which covers the exploitation of local privilege escalation vulnerabilities, and specifically relates to the use of kernel-mode exploits to gain system-level access. The attack vector typically involves a local user executing a specially crafted application that triggers the flawed impersonation handling in win32k.sys, allowing the attacker to escalate privileges without requiring additional attack surfaces or network connectivity. Microsoft classified this as a critical vulnerability due to its ease of exploitation and the high-impact privileges it can grant, making it a prime target for both automated exploitation tools and targeted attacks against vulnerable systems.
Mitigation strategies for CVE-2015-2527 primarily involve applying the official Microsoft security patches released in May 2015 as part of the Windows Update cycle. Organizations should prioritize patch deployment across all affected Windows versions, particularly in environments where local user access cannot be strictly controlled. Additional defensive measures include implementing least privilege principles, monitoring for unusual process behavior, and employing kernel-mode protection solutions such as Windows Defender Application Control or similar technologies that can prevent unauthorized code execution in kernel space. Network segmentation and user access controls should also be reinforced to limit the potential impact of successful exploitation attempts.