CVE-2025-47971: Windows 10 1507 Privilege Escalation Flaw

CVE-2025-47971 Overview

CVE-2025-47971 is a buffer over-read vulnerability in the Microsoft Windows Virtual Hard Disk (VHDX) component. The flaw allows an unauthorized local attacker to elevate privileges by triggering memory reads beyond the bounds of an allocated buffer. The weakness is classified under [CWE-126] (Buffer Over-read) and affects parsing logic used when Windows processes VHDX-formatted virtual disk files.

Successful exploitation requires local access and user interaction, typically by enticing a user to mount or open a crafted VHDX file. Microsoft addressed the issue in its July 2025 security update cycle.

Critical Impact

A local attacker who convinces a user to mount a malicious VHDX file can elevate privileges and gain high impact on confidentiality, integrity, and availability of the affected Windows host.

Affected Products

• Microsoft Windows 10 (1507, 1607, 1809, 21H2, 22H2) and Windows 11 (22H2, 23H2, 24H2)
• Microsoft Windows Server 2008, 2012, 2016, 2019, 2022, 2022 23H2, and 2025
• Both x86 and x64 editions where VHDX mounting is supported

Discovery Timeline

• 2025-07-08 - CVE-2025-47971 published to NVD
• 2025-07-14 - Last updated in NVD database

Technical Details for CVE-2025-47971

Vulnerability Analysis

The vulnerability resides in the code path responsible for parsing VHDX virtual disk metadata. A buffer over-read occurs when the parser reads past the end of an allocated buffer while processing crafted structures inside a VHDX file. Microsoft categorizes the issue as an elevation of privilege flaw, indicating that the out-of-bounds read can be leveraged to influence kernel-mode decisions and ultimately gain higher privileges on the local system.

The attack requires local access and user interaction. A standard user account is sufficient to trigger the vulnerable code path once a malicious VHDX file is mounted by the target.

Root Cause

The root cause is missing or insufficient bounds validation [CWE-126] when the VHDX driver reads structured data fields from a virtual disk image. When attacker-controlled length or offset values steer the parser to read beyond the buffer boundary, the resulting memory disclosure can leak kernel pointers, bypass mitigations such as KASLR, or feed corrupted data into subsequent processing that escalates privileges.

Attack Vector

The attack vector is local. An attacker delivers a malicious VHDX file to the target, for example through a phishing email, a removable drive, or a download from an attacker-controlled site. When the user double-clicks the file or otherwise mounts it through Windows Explorer or diskpart, the vulnerable parser processes the crafted metadata. The over-read enables the attacker to obtain information needed to escalate from a standard user context to a higher-privileged context on the host.

No public proof-of-concept exploit code has been published for CVE-2025-47971. Refer to the Microsoft Security Advisory CVE-2025-47971 for vendor technical detail.

Detection Methods for CVE-2025-47971

Indicators of Compromise

• Unexpected VHDX or VHD files dropped in user-writable locations such as %TEMP%, Downloads, or removable media
• Mount events for VHDX files originating from email attachments, archive extractions, or untrusted sources
• Process chains where Office applications, browsers, or archive utilities spawn vhdmp, diskpart, or PowerShell Mount-DiskImage activity

Detection Strategies

• Monitor Windows event logs for VHD/VHDX mount operations through the Microsoft-Windows-VHDMP provider and correlate with the originating parent process
• Hunt for PowerShell invocations of Mount-DiskImage, Mount-VHD, or New-PSDrive referencing VHDX files from non-administrative users
• Detect creation of .vhdx files immediately followed by a mount operation, a behavior pattern commonly associated with malware delivery using container files

Monitoring Recommendations

• Audit local privilege escalation telemetry on endpoints, particularly token elevation events following VHDX mount activity
• Track endpoints missing the July 2025 Microsoft security updates and prioritize remediation for systems where standard users routinely handle external files
• Forward VHDMP, Sysmon process creation, and kernel driver load events to a central data lake for correlation across the fleet

How to Mitigate CVE-2025-47971

Immediate Actions Required

• Apply the July 2025 Microsoft security updates that remediate CVE-2025-47971 across all affected Windows client and server SKUs
• Inventory hosts running unsupported editions such as Windows Server 2008 and 2012 and ensure they receive applicable extended security updates
• Restrict the ability of standard users to mount VHDX files from untrusted sources, particularly on servers and privileged workstations

Patch Information

Microsoft published the fix and detailed build information in the Microsoft Security Advisory CVE-2025-47971. Administrators should consult the advisory for the specific KB article and cumulative update applicable to each Windows version, then deploy through Windows Update, WSUS, Microsoft Update Catalog, or their preferred patch management workflow.

Workarounds

• Block delivery of VHD and VHDX attachments at the email gateway and web proxy where business workflows do not require them
• Configure Attack Surface Reduction rules and SmartScreen policies to limit execution of files dropped from disk image containers
• Disable automatic mounting of disk image files through Group Policy or file association changes where operationally feasible until patching is complete

# Example: block VHDX auto-mount via file association removal (PowerShell, run elevated)
Reg.exe delete "HKCR\Windows.VhdFile\shell\Mount" /f
Reg.exe delete "HKCR\Windows.VhdxFile\shell\Mount" /f