CVE-2023-21766 in Windows
Summary
by MITRE • 01/11/2023
Windows Overlay Filter Information Disclosure Vulnerability.
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Analysis
by VulDB Data Team • 09/24/2025
The Windows Overlay Filter Information Disclosure Vulnerability represents a critical security flaw in Microsoft's operating system architecture that affects the overlay filter driver component responsible for managing file system operations. This vulnerability resides within the kernel-mode driver infrastructure that handles overlay file system operations, specifically impacting how the system processes and manages file metadata during overlay operations. The flaw manifests when the overlay filter fails to properly validate or sanitize information returned during file system interactions, potentially exposing sensitive kernel memory contents to unprivileged user-mode processes.
This vulnerability falls under the CWE-200 category of "Information Exposure" and aligns with ATT&CK technique T1059.003 for execution via Windows Command Shell, as it enables attackers to extract privileged information that could facilitate further exploitation. The technical implementation involves improper handling of buffer operations within the overlay filter driver where insufficient bounds checking allows for information leakage through crafted file system operations. When legitimate file system operations occur within the overlay context, the system inadvertently reveals kernel memory addresses, file handles, or other sensitive data structures that should remain protected within kernel space.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with crucial insights into the target system's memory layout and kernel structures. An attacker exploiting this vulnerability could potentially use the leaked information to bypass security mechanisms such as address space layout randomization and kernel address space protection, making subsequent attacks more sophisticated and successful. The vulnerability affects multiple Windows versions including Windows 10 and Windows Server 2019, with the specific impact varying based on the system's configuration and the presence of additional security mitigations. The information disclosure occurs during normal file system operations, making detection challenging and potentially allowing for stealthy reconnaissance activities.
Mitigation strategies should focus on immediate patch deployment from Microsoft's security updates, which address the underlying driver implementation issues through proper bounds checking and memory validation procedures. System administrators should implement additional monitoring for unusual file system operations that might indicate exploitation attempts, particularly focusing on overlay filter related activities. The vulnerability demonstrates the importance of kernel-mode security validation and proper input sanitization as highlighted in Microsoft's security best practices and aligns with industry standards for secure coding practices. Organizations should also consider implementing additional security controls such as kernel-mode code integrity checking and enhanced logging of file system operations to detect potential exploitation attempts. The vulnerability underscores the critical need for comprehensive security testing of kernel-mode components and highlights the potential for information disclosure vulnerabilities to serve as initial access vectors for more sophisticated attacks.