CVE-2026-20825
📋 TL;DR
This CVE describes an improper access control vulnerability in Windows Hyper-V that allows an authenticated attacker with local access to a Hyper-V host to potentially disclose sensitive information from the hypervisor or other virtual machines. This affects organizations running Windows Hyper-V virtualization platforms.
💻 Affected Systems
- Windows Hyper-V
📦 What is this software?
Windows 10 1809 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 24h2 by Microsoft
Windows 11 25h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
An attacker could access sensitive data from other virtual machines or the hypervisor itself, potentially leading to credential theft, data exfiltration, or lateral movement within the virtual environment.
Likely Case
An authenticated attacker with local access could read memory or configuration data they shouldn't have access to, potentially exposing sensitive information about other VMs or the host system.
If Mitigated
With proper access controls and isolation, the impact is limited to information disclosure within the attacker's own virtual machine context.
🎯 Exploit Status
Requires local access and authentication to the Hyper-V host. The attacker needs to be able to execute code on the host system.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft's monthly security updates for the specific KB number
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20825
Restart Required: Yes
Instructions:
1. Apply the latest Windows security updates from Microsoft. 2. Restart the Hyper-V host system. 3. Verify the patch is applied using Windows Update history or system information.
🔧 Temporary Workarounds
Restrict Local Access
windowsLimit local access to Hyper-V hosts to only authorized administrators
Disable Hyper-V if Not Needed
windowsRemove the Hyper-V role/feature if virtualization is not required
Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-All
🧯 If You Can't Patch
- Implement strict access controls to limit who has local access to Hyper-V hosts
- Monitor Hyper-V host systems for unusual local access patterns or privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check if Hyper-V is enabled and verify Windows version against Microsoft's advisoryCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Check Windows Update history for the specific KB patch or verify system version matches patched version📡 Detection & Monitoring
Log Indicators:
- Unusual local login attempts to Hyper-V hosts
- Hyper-V service access from non-admin accounts
- Failed access attempts to hypervisor resources
Network Indicators:
- Not network exploitable - focus on host-based detection
SIEM Query:
EventID=4624 OR EventID=4625 with target host containing Hyper-V role and unusual account activity