CVE-2011-2005 in Windows
Summary
by MITRE
afd.sys in the Ancillary Function Driver in Microsoft Windows XP SP2 and SP3 and Server 2003 SP2 does not properly validate user-mode input passed to kernel mode, which allows local users to gain privileges via a crafted application, aka "Ancillary Function Driver Elevation of Privilege Vulnerability."
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Analysis
by VulDB Data Team • 04/22/2026
The vulnerability identified as CVE-2011-2005 resides within the afd.sys driver component of Microsoft Windows operating systems, specifically affecting Windows XP Service Pack 2 and 3 along with Windows Server 2003 Service Pack 2. This flaw represents a critical privilege escalation vulnerability that exploits the improper validation of user-mode input when it is passed to kernel mode through the Ancillary Function Driver. The afd.sys driver serves as a core component in Windows networking operations, handling socket operations and network communication functions that are essential for system networking capabilities.
The technical exploitation of this vulnerability stems from a lack of proper input validation within the kernel-mode driver code. When user applications interact with network functions through the Ancillary Function Driver, data flows from user mode into kernel mode where the driver processes these requests. The flaw occurs because the driver fails to adequately validate or sanitize input parameters before processing them in privileged kernel space. This inadequate validation creates a pathway for malicious applications to craft specific inputs that can manipulate the driver's behavior and execute arbitrary code with kernel-level privileges.
From an operational impact perspective, this vulnerability enables local attackers who already have user-level access to escalate their privileges to SYSTEM level, which represents the highest privilege level in Windows operating systems. The exploitation process typically involves creating a malicious application that carefully constructs input parameters to trigger the validation bypass in afd.sys. Once successful, the attacker gains complete control over the affected system, allowing for persistent access, data exfiltration, system modification, and potential lateral movement within network environments. The vulnerability is particularly dangerous because it requires no special privileges to exploit, making it accessible to any user with local access to the compromised system.
The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and represents a classic example of improper input validation in kernel-mode drivers. According to MITRE ATT&CK framework, this vulnerability maps to privilege escalation techniques under the T1068 category, specifically targeting the exploitation of kernel-mode vulnerabilities to achieve system-level access. Organizations affected by this vulnerability face significant risk as it can be leveraged in various attack scenarios including persistent threats, insider attacks, and automated exploitation campaigns. The vulnerability demonstrates the critical importance of kernel-mode input validation and proper privilege separation between user and kernel space in operating system security design.
Microsoft addressed this vulnerability through security update MS11-046, which provided patches to fix the input validation issues in the afd.sys driver. The mitigation strategy involves applying the relevant security update promptly and ensuring that systems are properly maintained with current security patches. System administrators should also implement additional security controls including user access restrictions, network segmentation, and monitoring for suspicious system behavior that might indicate exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify systems that may be running unpatched versions of the affected operating systems, as the vulnerability remains exploitable on systems that have not received the necessary security updates.