CVE-2025-21335: Windows Hyper-V Privilege Escalation Flaw

CVE-2025-21335 Overview

Windows Hyper-V NT Kernel Integration VSP Elevation of Privilege Vulnerability

Critical Impact

This vulnerability affects multiple versions of Microsoft Windows and can lead to elevation of privilege with significant impact on confidentiality, integrity, and availability.

Affected Products

• Microsoft Windows 10 21H2
• Microsoft Windows 11 22H2
• Microsoft Windows Server 2022 23H2

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to Microsoft
• Not Available - CVE CVE-2025-21335 assigned
• Not Available - Microsoft releases security patch
• 2025-01-14T18:15:58.960 - CVE CVE-2025-21335 published to NVD
• 2025-10-27T17:13:16.927 - Last updated in NVD database

Technical Details for CVE-2025-21335

Vulnerability Analysis

The vulnerability lies in the Windows Hyper-V NT Kernel Integration Virtual Service Provider (VSP), which allows an attacker with local access to exploit a privilege escalation flaw. The issue arises due to improper memory handling, specifically a Use After Free condition, which can potentially be leveraged to execute arbitrary code with elevated privileges.

Root Cause

The root cause of the vulnerability is a Use After Free condition in the Windows Hyper-V NT Kernel Integration VSP, leading to unauthorized access to sensitive resources.

Attack Vector

The attack vector is local, requiring the attacker to have local access to the affected system to exploit the vulnerability.

// Example exploitation code (sanitized)
#include <windows.h>

void exploit() {
    // Placeholder code to simulate UAF exploit scenario
    HANDLE handle = CreateFile("\\.\\VulnerableDevice", 
                              GENERIC_READ | GENERIC_WRITE, 
                              0, 
                              NULL, 
                              OPEN_EXISTING, 
                              FILE_ATTRIBUTE_NORMAL, 
                              NULL);
    if (handle != INVALID_HANDLE_VALUE) {
        // Simulated vulnerability trigger
        CloseHandle(handle);
        // Use handle after it has been closed
    }
}

Detection Methods for CVE-2025-21335

Indicators of Compromise

• Unusual system file accesses by non-admin users
• Unexpected service restarts
• Altered permissions on critical system files

Detection Strategies

Utilize endpoint detection and response (EDR) solutions to monitor and alert on suspicious process activities and file alterations related to system-level components.

Monitoring Recommendations

Implement comprehensive monitoring of system calls related to the Hyper-V integration services. SentinelOne's behavioral AI can detect anomalies indicative of exploitation attempts.

How to Mitigate CVE-2025-21335

Immediate Actions Required

• Restrict local access to the affected systems
• Implement stringent user access controls
• Monitor systems for suspicious activities

Patch Information

Refer to Microsoft's advisory for the latest patches: Microsoft Security Update Guide

Workarounds

Limit the functionality of VSP where applicable and ensure robust disaster recovery procedures are in place to mitigate potential impacts.

# Configuration example to disable certain services
Stop-Service -Name "VulnerableService" -Force
Set-Service -Name "VulnerableService" -StartupType Disabled