CVE-2022-21958: Windows ReFS RCE Vulnerability

CVE-2022-21958 Overview

CVE-2022-21958 is a Remote Code Execution vulnerability affecting the Windows Resilient File System (ReFS) component across a wide range of Microsoft Windows operating systems. This vulnerability requires physical access to an affected system to exploit, allowing an attacker to execute arbitrary code with elevated privileges once they gain physical access to a vulnerable machine.

ReFS (Resilient File System) is Microsoft's modern file system designed for data availability, scalability, and integrity. A flaw in the ReFS driver allows attackers with physical access to craft malicious input that triggers code execution in the context of the operating system kernel.

Critical Impact

Successful exploitation allows attackers with physical access to execute arbitrary code, potentially gaining complete control over the affected system with the ability to read, modify, or delete data and install persistent malware.

Affected Products

• Microsoft Windows 10 (all versions including 1607, 1809, 1909, 20H2, 21H1, 21H2)
• Microsoft Windows 11 (x64 and ARM64)
• Microsoft Windows 8.1 and Windows RT 8.1
• Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 20H2

Discovery Timeline

• January 11, 2022 - CVE-2022-21958 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-21958

Vulnerability Analysis

This vulnerability exists within the Windows Resilient File System (ReFS) driver, which handles file system operations for ReFS-formatted volumes. The flaw allows an attacker with physical access to the system to execute arbitrary code at the kernel level, bypassing standard security controls.

The attack requires physical access to the target machine, meaning an attacker must be able to interact directly with the hardware. Once physical access is obtained, the attacker can leverage this vulnerability to compromise the system's integrity, confidentiality, and availability completely. The exploitation does not require authentication or user interaction, making it particularly dangerous in scenarios where physical security controls are weak.

Root Cause

While Microsoft has not disclosed specific technical details about the root cause (classified as NVD-CWE-noinfo), vulnerabilities of this nature in file system drivers typically stem from improper validation of file system metadata, buffer handling errors when processing malformed ReFS structures, or memory corruption issues triggered by crafted file system images.

The ReFS driver operates at the kernel level with elevated privileges. Any code execution vulnerability in this component inherently provides attackers with kernel-level access, enabling complete system compromise.

Attack Vector

The physical attack vector (AV:P) indicates that exploitation requires direct physical access to the target system. Attack scenarios include:

An attacker could connect a malicious USB storage device formatted with a crafted ReFS volume that exploits the vulnerability when Windows attempts to mount or parse the file system. Alternatively, an attacker with physical access to an unlocked or booted system could mount a malicious disk image or connect external storage containing the exploit payload.

The vulnerability requires no privileges on the target system and no user interaction beyond the automatic file system parsing that occurs when storage devices are connected.

Detection Methods for CVE-2022-21958

Indicators of Compromise

• Unexpected ReFS volume mount operations or file system driver activity
• Unusual kernel-mode crashes or blue screens related to refs.sys driver
• Unauthorized external storage device connections in Windows Event Logs
• Suspicious processes spawned with SYSTEM privileges following storage device connections

Detection Strategies

• Monitor Windows Event Logs for ReFS-related errors or unexpected volume mount events (Event IDs in the storage subsystem category)
• Implement endpoint detection rules for suspicious kernel driver behavior and unexpected code execution from file system operations
• Deploy USB device control policies to alert on unauthorized removable media connections
• Configure SentinelOne to detect anomalous kernel-mode activity and privilege escalation attempts

Monitoring Recommendations

• Enable detailed logging for Plug and Play events and storage device connections
• Monitor for ReFS driver (refs.sys) crashes or exceptions using Windows Error Reporting
• Implement physical security monitoring and access controls for sensitive systems
• Use SentinelOne's behavioral AI to detect post-exploitation activity such as persistence mechanisms or lateral movement

How to Mitigate CVE-2022-21958

Immediate Actions Required

• Apply the latest Microsoft security updates from January 2022 Patch Tuesday immediately
• Restrict physical access to critical systems and implement strong physical security controls
• Disable auto-mount functionality for removable storage devices where operationally feasible
• Implement USB device control policies to prevent unauthorized storage device connections

Patch Information

Microsoft released security patches addressing this vulnerability as part of the January 2022 security updates. Organizations should download and apply the appropriate cumulative update for their Windows version from the Microsoft Update Guide or through Windows Update and WSUS.

For detailed patch information and affected version-specific updates, refer to the Microsoft Security Advisory for CVE-2022-21958.

Workarounds

• Implement strict physical access controls to prevent unauthorized persons from accessing vulnerable systems
• Configure Group Policy to disable automatic mounting of removable storage: Computer Configuration > Administrative Templates > System > Removable Storage Access
• Use BitLocker or similar full-disk encryption to protect systems in case of physical compromise
• Deploy USB device whitelisting to only allow known, trusted storage devices

# Disable automatic mounting of new volumes via registry
reg add "HKLM\SYSTEM\CurrentControlSet\Services\MountMgr" /v NoAutoMount /t REG_DWORD /d 1 /f

# Verify the setting is applied
reg query "HKLM\SYSTEM\CurrentControlSet\Services\MountMgr" /v NoAutoMount