CVE-2025-29833
📋 TL;DR
A Time-of-Check Time-of-Use (TOCTOU) race condition vulnerability in Windows Virtual Machine Bus allows local attackers to execute arbitrary code. This affects Windows systems using Hyper-V virtualization. Attackers must have local access to exploit this vulnerability.
💻 Affected Systems
- Windows Hyper-V
- Windows Virtual Machine Bus
📦 What is this software?
Windows 10 1507 by Microsoft
Windows 10 1507 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 11 22h2 by Microsoft
Windows 11 22h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 24h2 by Microsoft
Windows 11 24h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining SYSTEM privileges, enabling persistence, lateral movement, and data exfiltration.
Likely Case
Local privilege escalation allowing attackers to elevate from standard user to SYSTEM privileges on affected Windows systems.
If Mitigated
Limited impact with proper access controls, network segmentation, and Hyper-V isolation preventing successful exploitation.
🎯 Exploit Status
Requires local access and precise timing to trigger race condition. Exploitation may be challenging but feasible for skilled attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update Guide for specific KB numbers
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-29833
Restart Required: Yes
Instructions:
1. Apply latest Windows security updates via Windows Update. 2. For enterprise: Deploy patches through WSUS, SCCM, or Intune. 3. Restart affected systems after patch installation.
🔧 Temporary Workarounds
Disable Hyper-V
windowsDisable Hyper-V virtualization features if not required
Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-All
Restrict Local Access
allImplement strict access controls to limit local user privileges
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Hyper-V hosts
- Enable Windows Defender Application Control or similar application whitelisting
🔍 How to Verify
Check if Vulnerable:
Check if Hyper-V is enabled and system is unpatched via: Get-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-AllCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify Windows Update history for relevant security patches and check system version📡 Detection & Monitoring
Log Indicators:
- Unusual process creation from vmbus related processes
- Failed privilege escalation attempts
- Suspicious Hyper-V service activity
Network Indicators:
- Not applicable - local exploitation only
SIEM Query:
Process Creation where (Image contains 'vmbus' OR ParentImage contains 'vmbus') AND CommandLine contains suspicious patterns