CVE-2011-0086 in Windows
Summary
by MITRE
win32k.sys in the kernel-mode drivers in Microsoft Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 Gold, SP2, and R2, and Windows 7 does not properly validate user-mode input, which allows local users to gain privileges via a crafted application, aka "Win32k Improper User Input Validation Vulnerability."
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Analysis
by VulDB Data Team • 03/18/2021
The CVE-2011-0086 vulnerability represents a critical privilege escalation flaw within the Windows kernel-mode driver subsystem, specifically in the win32k.sys component that manages user interface elements and graphics operations. This vulnerability exists in multiple Windows operating system versions including XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 Gold, SP2, and R2, as well as Windows 7. The flaw stems from inadequate validation of user-mode input parameters passed to kernel-mode functions, creating a pathway for malicious applications to exploit the system's security boundaries.
The technical mechanism of this vulnerability involves improper validation of user-mode input within the win32k.sys driver which handles window management, graphics rendering, and user interface operations. When applications interact with the Windows graphical subsystem, they pass parameters through kernel-mode interfaces that should be rigorously validated before processing. However, the win32k.sys driver fails to adequately validate these parameters, allowing attackers to craft malicious input that can manipulate kernel-mode memory structures. This improper validation creates a condition where user-mode applications can influence kernel-mode execution flow, effectively bridging the security boundary between user and kernel contexts.
The operational impact of this vulnerability is severe as it enables local privilege escalation attacks that can elevate a standard user account to SYSTEM level privileges. Attackers can leverage this vulnerability by creating a malicious application that exploits the input validation flaw in win32k.sys, allowing them to execute arbitrary code with the highest system privileges. This privilege escalation capability means that an attacker with limited user access can gain complete control over the affected system, potentially leading to data theft, system compromise, or further network infiltration. The vulnerability is particularly dangerous because it operates at the kernel level where all system security mechanisms are bypassed, making traditional defenses ineffective against such attacks.
This vulnerability maps directly to CWE-121, which describes "Stack-based Buffer Overflow" and CWE-122, which covers "Heap-based Buffer Overflow," though the specific implementation involves improper input validation rather than direct buffer overflows. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1068, "Exploitation for Privilege Escalation," and T1059, "Command and Scripting Interpreter," as attackers can leverage the elevated privileges to execute additional malicious code. The attack surface is extensive given the wide range of affected operating systems, making this vulnerability particularly impactful in enterprise environments where multiple Windows versions may be deployed. Microsoft addressed this vulnerability through kernel-mode input validation improvements and enhanced security boundaries between user and kernel modes, emphasizing the critical importance of proper input validation in kernel-mode drivers.
Organizations should implement immediate mitigations including applying the relevant security updates, implementing application whitelisting policies to prevent execution of untrusted code, and monitoring for suspicious privilege escalation activities. The vulnerability demonstrates the critical importance of robust kernel-mode security practices and proper input validation mechanisms in preventing privilege escalation attacks that can compromise entire operating systems.