CVE-2011-1876 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 CVEs listed in MS11-054, aka "Win32k Use After Free Vulnerability."
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Analysis
by VulDB Data Team • 11/14/2021
The CVE-2011-1876 vulnerability represents a critical use-after-free flaw in the win32k.sys kernel-mode driver component of Microsoft Windows operating systems. This vulnerability resides within the graphics subsystem's kernel driver responsible for managing user interface elements, window management, and graphics operations. The flaw specifically manifests in how the driver handles reference counting and object lifecycle management when processing certain graphics operations, creating a scenario where freed memory objects can still be accessed by malicious code. This particular vulnerability affects a broad range of Microsoft Windows versions including Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP1 and SP2, Windows Server 2008 in various service pack configurations, and Windows 7 Gold and SP1 releases.
The technical implementation of this vulnerability stems from improper management of driver object references within the win32k.sys module. When a legitimate application creates or manipulates graphics objects such as windows, brushes, or pens, the kernel driver maintains internal reference counts to track object usage. However, in certain code paths involving specific graphics operations and window management functions, the driver fails to properly decrement reference counts or properly handle object cleanup, leading to situations where memory allocated to graphics objects is freed but the system continues to reference that memory location. This creates a race condition where malicious code can potentially overwrite the freed memory with malicious data and then trigger the use-after-free condition during subsequent operations, allowing execution of arbitrary code in kernel mode. The vulnerability operates at the kernel level, making it particularly dangerous as it can be exploited to escalate privileges from user-level processes to SYSTEM level privileges. This aligns with CWE-416, which describes the use of freed memory condition, and represents a classic example of improper object lifecycle management in kernel-mode drivers.
The operational impact of CVE-2011-1876 is severe and multifaceted, as it provides local attackers with a pathway to privilege escalation without requiring network connectivity or complex exploitation techniques. Attackers can leverage this vulnerability through a crafted application that mimics legitimate graphics operations, making the attack vector relatively simple to implement. Once successfully exploited, the vulnerability allows attackers to execute code with the highest privileges available to the operating system, effectively compromising the entire system. The attack requires local system access, meaning an attacker must already have a user account on the target system, but the privilege escalation capability makes this vulnerability particularly attractive for attackers who have already gained initial access. The vulnerability's impact extends beyond simple code execution, as it can be used to establish persistent backdoors, disable security features, or extract sensitive information from the compromised system. According to ATT&CK framework, this vulnerability maps to privilege escalation techniques and can be categorized under T1068, which covers 'Exploitation for Privilege Escalation' and T1543, 'Create or Modify System Process' as attackers may attempt to establish persistence through kernel-level modifications.
Mitigation strategies for CVE-2011-1876 focus primarily on applying the Microsoft security patch released as part of MS11-054, which addresses the underlying driver object management issues. Organizations should prioritize immediate deployment of the security update across all affected systems, particularly those running older Windows versions such as Windows XP and Server 2003 that are no longer receiving extended support. System administrators should also implement additional security controls including disabling unnecessary graphics functionality, monitoring for suspicious graphics-related process activity, and maintaining updated endpoint protection solutions that can detect anomalous behavior associated with kernel-mode exploitation attempts. Network segmentation and privilege minimization practices can reduce the potential impact of successful exploitation, while regular security assessments and vulnerability scanning should be conducted to identify systems running unsupported Windows versions that may be vulnerable to similar kernel-mode flaws. The vulnerability demonstrates the critical importance of proper kernel-mode memory management and object lifecycle handling, which serves as a reminder of the inherent risks associated with complex driver code and the need for robust security testing of system-level components.