CVE-2011-0088 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 Window Class Pointer Confusion Vulnerability."
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Analysis
by VulDB Data Team • 10/16/2021
The CVE-2011-0088 vulnerability represents a critical privilege escalation flaw within the Windows kernel-mode driver component known as win32k.sys. This vulnerability affects multiple versions of the Windows operating system including Windows 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 resides in how the kernel-mode drivers handle user-mode input validation, creating a pathway for local attackers to execute arbitrary code with elevated privileges. The vulnerability specifically exploits the improper validation of window class pointers within the win32k.sys driver, which governs the graphical user interface components of Windows. This type of vulnerability falls under the Common Weakness Enumeration category CWE-125, which describes "Out-of-bounds Read" conditions where memory is accessed beyond its allocated bounds. The attack vector requires local system access, making it particularly dangerous as it can be exploited by malicious software already present on the system or by an attacker who has already achieved a foothold through other means.
The technical exploitation of this vulnerability occurs through a sophisticated manipulation of window class pointer structures in the Windows kernel. When a malicious application attempts to create or modify window class objects, the win32k.sys driver fails to properly validate the user-mode input parameters, leading to a pointer confusion scenario. This allows attackers to manipulate kernel memory pointers and potentially overwrite critical system structures. The vulnerability specifically targets the interaction between user-mode applications and kernel-mode drivers, where the driver should enforce strict validation of all input parameters but instead permits malformed data to propagate into kernel space. This type of flaw represents a classic example of a kernel-mode privilege escalation vulnerability that can be leveraged to bypass security controls and gain SYSTEM-level privileges. The ATT&CK framework categorizes this under T1068, "Exploitation for Privilege Escalation," where adversaries exploit vulnerabilities in operating systems or applications to gain higher levels of access. The impact is severe as successful exploitation allows attackers to execute code with the highest privileges available on the system, potentially enabling complete system compromise and persistent access.
The operational impact of CVE-2011-0088 extends far beyond simple privilege escalation, as it provides attackers with the capability to establish persistent backdoors, exfiltrate sensitive data, and deploy additional malware without detection. Once an attacker achieves SYSTEM-level privileges through this vulnerability, they can modify system files, disable security services, and create new user accounts with administrative privileges. The vulnerability's presence across multiple Windows versions means that organizations running any of the affected operating systems are at risk, regardless of their security measures. The exploitation typically requires a local attacker with standard user privileges, but the resulting SYSTEM access provides complete control over the compromised system. Organizations that have not patched their systems remain vulnerable to both automated exploitation tools and targeted attacks by sophisticated threat actors. The vulnerability's classification as a kernel-mode privilege escalation flaw means that traditional endpoint protection solutions may not detect the exploitation attempts, as the malicious activity occurs within the kernel space where normal security monitoring is limited. This vulnerability has been widely exploited in the wild, particularly in targeted attacks against enterprise networks where attackers first establish a foothold before leveraging this privilege escalation capability to move laterally within the network. The remediation process requires immediate patching of all affected systems, as the vulnerability cannot be effectively mitigated through configuration changes or network security controls alone.
Microsoft addressed this vulnerability through security update MS11-008, which corrected the improper validation of user-mode input in the win32k.sys driver. The patch implemented proper bounds checking and input validation mechanisms to prevent the pointer confusion scenario that enabled privilege escalation. Organizations should ensure that all systems running affected versions of Windows are updated with the latest security patches, as the vulnerability remains exploitable on unpatched systems. The vulnerability also highlights the importance of maintaining up-to-date security patches and implementing robust vulnerability management processes to prevent exploitation of known vulnerabilities. Security professionals should monitor for exploitation attempts using endpoint detection and response tools, as the kernel-mode nature of the vulnerability makes traditional network-based detection challenging. The CVE-2011-0088 vulnerability serves as a reminder of the critical importance of kernel-mode security and the potential consequences when input validation fails in core operating system components. Organizations should implement comprehensive security monitoring and incident response procedures to detect and respond to exploitation attempts, as the vulnerability can be leveraged for significant operational damage when successfully exploited. The remediation process should include not only patching but also network segmentation and access control measures to limit the potential impact of successful exploitation attempts.