CVE-2011-1239 in Windows
Summary
by MITRE
Use-after-free vulnerability in 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, R2, and R2 SP1, and Windows 7 Gold and SP1 allows local users to gain privileges via a crafted application that leverages incorrect driver object management, a different vulnerability than other "Vulnerability Type 1" CVEs listed in MS11-034, aka "Win32k Use After Free Vulnerability."
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Analysis
by VulDB Data Team • 05/11/2025
The CVE-2011-1239 vulnerability represents a critical use-after-free condition in the win32k.sys kernel-mode driver component of Microsoft Windows operating systems. This flaw exists within the windowing subsystem that manages graphical user interface elements, making it a prime target for privilege escalation attacks. The vulnerability affects a broad range of Windows versions including XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 Gold, SP2, R2, and R2 SP1, as well as Windows 7 Gold and SP1, demonstrating the widespread impact of this kernel-level flaw. The vulnerability specifically manifests when the win32k.sys driver improperly manages driver object references, creating opportunities for malicious code to exploit the freed memory locations.
This use-after-free vulnerability operates through incorrect driver object management within the kernel-mode environment, where a freed memory block is accessed after it has been deallocated by the system. The flaw allows local attackers to craft malicious applications that can manipulate the windowing subsystem to trigger the vulnerable code path. The vulnerability is classified as a different type from other "Vulnerability Type 1" CVEs in MS11-034, indicating it represents a distinct exploitation vector despite sharing similar targeting characteristics. The kernel-mode nature of win32k.sys means that successful exploitation can result in complete system compromise, as the attacker gains access to the most privileged execution context within the operating system.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass full system compromise capabilities. Attackers can leverage the use-after-free condition to execute arbitrary code with kernel-level privileges, potentially enabling them to install persistent backdoors, modify system files, disable security features, or establish covert communication channels. The attack requires local system access, making it particularly dangerous in environments where users might have elevated privileges or where privilege escalation opportunities exist through other means. The vulnerability's exploitation can lead to complete system takeover, data exfiltration, and establishment of persistent access points that are difficult to detect and remove.
Security mitigations for CVE-2011-1239 primarily focus on applying Microsoft's security patches and updates, which address the underlying driver object management issues in win32k.sys. System administrators should prioritize immediate patch deployment across all affected Windows versions, as the vulnerability was widely exploited in the wild during its active period. Additional protective measures include implementing application whitelisting policies, disabling unnecessary graphical services, and monitoring for suspicious kernel-mode activity. From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1068 for privilege escalation and T1059 for command execution, while the underlying CWE-416 represents the specific weakness in memory management. Organizations should also consider implementing endpoint detection and response solutions capable of identifying anomalous kernel-mode behavior patterns that may indicate exploitation attempts.