CVE-2021-27061
📋 TL;DR
CVE-2021-27061 is a remote code execution vulnerability in Microsoft's HEVC Video Extensions that allows attackers to execute arbitrary code by tricking users into opening specially crafted media files. This affects Windows systems with the HEVC Video Extensions installed, typically through the Microsoft Store. Users who open malicious video files are at risk.
💻 Affected Systems
- HEVC Video Extensions from Microsoft Store
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the affected system, potentially leading to data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Local user account compromise when a user opens a malicious video file, allowing attackers to execute code with the user's privileges and potentially escalate to higher privileges.
If Mitigated
Limited impact with proper application whitelisting, restricted user privileges, and network segmentation preventing lateral movement.
🎯 Exploit Status
Exploitation requires user interaction (opening a malicious file). No public exploit code was available at the time of disclosure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Updated version available through Microsoft Store
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-27061
Restart Required: No
Instructions:
1. Open Microsoft Store. 2. Click on 'Library' in bottom left. 3. Click 'Get updates' to update all apps. 4. Alternatively, search for 'HEVC Video Extensions' and update manually.
🔧 Temporary Workarounds
Uninstall HEVC Video Extensions
windowsRemove the vulnerable component entirely if not needed for business operations
Get-AppxPackage *HEVC* | Remove-AppxPackage
Disable automatic media file opening
windowsConfigure Windows to not automatically open media files from untrusted sources
🧯 If You Can't Patch
- Implement application control policies to block execution of HEVC Video Extensions
- Educate users about the risks of opening media files from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check HEVC Video Extensions version in Microsoft Store or via PowerShell: Get-AppxPackage *HEVC* | Select Name, VersionCheck Version:
Get-AppxPackage *HEVC* | Select Name, VersionVerify Fix Applied:
Verify HEVC Video Extensions version is updated to February 2021 or later release📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing HEVC Video Extensions crashes
- Application logs showing unexpected media file processing
Network Indicators:
- Unusual outbound connections following media file opening
- DNS requests to suspicious domains after video playback
SIEM Query:
EventID=1000 AND Source='Application Error' AND ProcessName LIKE '%HEVC%'