CVE-2021-1672 in Windows
Summary
by MITRE • 01/13/2021
Windows Projected File System FS Filter Driver Information Disclosure Vulnerability This CVE ID is unique from CVE-2021-1663, CVE-2021-1670.
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Analysis
by VulDB Data Team • 10/09/2024
The Windows Projected File System FS Filter Driver Information Disclosure Vulnerability represents a critical security flaw within Microsoft's file system filtering infrastructure that affects multiple Windows operating systems including Windows 10, Windows Server 2016, and Windows Server 2019. This vulnerability resides in the projected file system filter driver component that handles virtualized file system operations and enables applications to present data as files without actually storing them on disk. The flaw specifically manifests in how the driver processes certain file system requests and manages memory structures during projected file operations, creating an information disclosure condition that could potentially expose sensitive kernel memory contents to unprivileged users.
The technical implementation of this vulnerability stems from improper validation of input parameters within the FS filter driver's handling of projected file system operations. When applications attempt to access projected files through the Windows file system interface, the driver fails to properly sanitize certain data structures that contain kernel memory addresses and internal driver state information. This occurs during the processing of specific file system control codes and operations that involve virtualized file representations, where the driver inadvertently leaks information about kernel memory layout and internal driver data structures. The vulnerability is classified under CWE-200 as an information disclosure flaw, specifically related to improper handling of sensitive data within kernel mode components. Attackers can leverage this weakness by crafting specific file system operations that trigger the vulnerable code path, potentially exposing kernel memory contents that could aid in further exploitation attempts.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates opportunities for advanced persistent threat actors to gather intelligence about the target system's kernel memory layout and driver state. This information leakage could facilitate more sophisticated attacks by providing attackers with insights into system internals that would normally remain hidden from user-mode processes. The vulnerability affects systems running Windows 10 versions 1909, 2004, and 20H2, as well as Windows Server 2016 and 2019, making it particularly concerning for enterprise environments where these operating systems are prevalent. The information disclosure occurs at the kernel level and can potentially expose sensitive driver data structures, memory addresses, and internal state information that could be used to bypass security mitigations such as kernel address space layout randomization. From an ATT&CK framework perspective, this vulnerability maps to technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, as it provides a potential pathway for attackers to gather information for more advanced exploitation techniques.
Mitigation strategies for this vulnerability primarily focus on applying the official Microsoft security updates that address the specific memory handling issues within the projected file system filter driver. Organizations should prioritize deployment of the relevant Windows updates, particularly those released in the January 2021 security bulletin, which contain patches specifically targeting this information disclosure flaw. System administrators should also implement additional monitoring measures to detect unusual file system access patterns that might indicate exploitation attempts, particularly focusing on projected file system operations and virtualized file access patterns. Network segmentation and privilege separation can help limit the potential impact of successful exploitation attempts, while regular security assessments should include checks for proper patch management and monitoring of kernel memory access patterns. The vulnerability demonstrates the importance of proper kernel memory management and input validation in file system drivers, as highlighted in Microsoft's security best practices documentation and aligned with the principles outlined in the CWE database for information disclosure vulnerabilities.