CVE-2025-49751
📋 TL;DR
A missing synchronization vulnerability in Windows Hyper-V allows authenticated attackers on adjacent networks to cause denial of service conditions. This affects organizations running Hyper-V virtualization on Windows Server and Windows client systems. Attackers must have network access to the Hyper-V host and appropriate authentication.
💻 Affected Systems
- Windows Hyper-V
📦 What is this software?
Windows 10 1607 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 11 22h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 24h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete disruption of all virtual machines running on the Hyper-V host, causing extended downtime and potential data loss from unsaved operations.
Likely Case
Temporary service degradation or crashes affecting specific virtual machines or Hyper-V management functions.
If Mitigated
Limited impact due to network segmentation and proper authentication controls preventing adjacent network access.
🎯 Exploit Status
Requires authentication and adjacent network access. Synchronization vulnerabilities typically require specific timing conditions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: To be determined from Microsoft's monthly security updates
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-49751
Restart Required: No
Instructions:
1. Check Microsoft Security Update Guide for CVE-2025-49751. 2. Apply the appropriate Windows security update for your version. 3. Verify Hyper-V services are functioning post-update.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Hyper-V management networks from general user networks to limit adjacent access
Authentication Hardening
allImplement strict authentication requirements and monitor for unusual access patterns
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Hyper-V hosts from untrusted networks
- Enhance monitoring for Hyper-V service disruptions and authentication anomalies
🔍 How to Verify
Check if Vulnerable:
Check Windows version and Hyper-V status via PowerShell: Get-WindowsFeature -Name Hyper-VCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify Windows Update history contains the relevant security update and Hyper-V services are stable📡 Detection & Monitoring
Log Indicators:
- Unexpected Hyper-V service crashes
- Authentication failures to Hyper-V management interfaces
- Performance counters showing Hyper-V resource exhaustion
Network Indicators:
- Unusual traffic patterns to Hyper-V management ports (5985, 5986, 2179)
SIEM Query:
EventID=7031 OR EventID=1000 AND SourceName="Hyper-V*" OR ProcessName="vmms.exe"