CVE-2022-21958 Overview
CVE-2022-21958 is a remote code execution vulnerability in the Windows Resilient File System (ReFS) driver. The flaw affects multiple Windows client and server versions, including Windows 10, Windows 11, Windows 8.1, Windows RT 8.1, and Windows Server 2012 through 2022. Exploitation requires physical access to the target system, which limits the attack surface but does not eliminate risk in shared, kiosk, or unattended-device scenarios. Successful exploitation can lead to arbitrary code execution with high impact on confidentiality, integrity, and availability. Microsoft addressed the issue through its January 2022 security update cycle.
Critical Impact
An attacker with physical access to a system can mount a crafted ReFS volume to execute arbitrary code and fully compromise the host.
Affected Products
- Microsoft Windows 10 (multiple builds: 1607, 1809, 1909, 20H2, 21H1, 21H2) on x86, x64, and ARM64
- Microsoft Windows 11, Windows 8.1, and Windows RT 8.1
- Microsoft Windows Server 2012, Server 2012 R2, Server 2016, Server 2019, Server 20H2, and Server 2022
Discovery Timeline
- 2022-01-11 - CVE-2022-21958 published to NVD and addressed in Microsoft's January 2022 security update
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2022-21958
Vulnerability Analysis
The vulnerability resides in the Windows ReFS file system driver, which parses on-disk metadata structures when a volume is mounted or accessed. A crafted ReFS volume can trigger memory corruption in the driver, leading to code execution in the kernel or another privileged context. Microsoft classifies the issue as remote code execution despite the physical attack vector because the malicious data originates outside the trust boundary of the host. The CWE assignment is NVD-CWE-noinfo, indicating Microsoft did not publish detailed root-cause classification.
Root Cause
The root cause lies in how the ReFS driver handles malformed file system structures during volume parsing. When the driver processes attacker-controlled metadata, insufficient validation allows corruption of kernel data structures. Microsoft has not released the specific code-level details of the flaw.
Attack Vector
Exploitation requires physical access. An attacker connects a removable storage device, such as a USB drive formatted with a malicious ReFS volume, to the target system. When Windows mounts and parses the crafted volume, the vulnerable driver code path executes. No user interaction beyond the mount is required, and no prior authentication is needed. Environments with auto-mount enabled, unattended workstations, and shared-use devices represent the primary risk surface.
// No verified proof-of-concept code is publicly available for CVE-2022-21958.
// Refer to the Microsoft Security Response Center advisory for technical context.
Stop Remote Code Execution Before It Runs
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Stop Exploit AttemptsDetection Methods for CVE-2022-21958
Indicators of Compromise
- Unexpected mounting of ReFS-formatted removable media on systems that do not normally use ReFS volumes
- Kernel-mode crashes or bug checks referencing the ReFS driver (refs.sys or refsv1.sys) in Windows Event Logs
- Unauthorized USB or external storage device connections recorded in Microsoft-Windows-DriverFrameworks-UserMode/Operational logs
Detection Strategies
- Monitor Windows Event ID 6416 (new external device recognized) and correlate with file system mount events for ReFS volumes
- Alert on processes spawning from System context immediately after a removable media insertion event
- Inspect crash dumps for faulting modules matching the ReFS driver as a possible exploitation signal
Monitoring Recommendations
- Enable USB and removable storage auditing via Group Policy and forward events to a centralized SIEM for correlation
- Track patch deployment status for KB articles from the January 2022 security update across all Windows endpoints and servers
- Baseline ReFS usage in the environment so anomalous ReFS volume mounts trigger investigation
How to Mitigate CVE-2022-21958
Immediate Actions Required
- Apply the January 2022 Microsoft security update to all affected Windows client and server systems
- Inventory endpoints with physical exposure (kiosks, shared workstations, conference room PCs) and prioritize patching
- Disable auto-mount of removable storage on high-value systems where USB usage is not required
Patch Information
Microsoft released a patch addressing CVE-2022-21958 in the January 11, 2022 security update. Administrators should consult the Microsoft CVE-2022-21958 Update Guide and the Microsoft Security Advisory for the specific KB articles applicable to each Windows build.
Workarounds
- Restrict physical access to systems through facility controls, locking ports, and tamper-evident seals
- Block USB mass storage devices via Group Policy on systems that do not require removable media
- Configure Windows to require administrative approval before mounting unknown file system volumes
# Group Policy path to disable removable storage access on Windows endpoints
# Computer Configuration > Administrative Templates > System > Removable Storage Access
# Set: "All Removable Storage classes: Deny all access" = Enabled
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
