CVE-2021-27047
📋 TL;DR
CVE-2021-27047 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 of complete system compromise.
💻 Affected Systems
- HEVC Video Extensions from Microsoft Store
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system takeover with administrative privileges, allowing data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Local user account compromise leading to data exfiltration, credential theft, and lateral movement within the network.
If Mitigated
Limited impact with proper application whitelisting and user education preventing malicious file execution.
🎯 Exploit Status
Exploitation requires user interaction to open malicious media file. No public exploit code was available at disclosure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Update through Microsoft Store (automatic updates enabled)
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-27047
Restart Required: No
Instructions:
1. Open Microsoft Store 2. Click 'Library' 3. Click 'Get updates' 4. Install HEVC Video Extensions update 5. Alternatively, enable automatic updates in Microsoft Store settings
🔧 Temporary Workarounds
Uninstall HEVC Video Extensions
windowsRemove the vulnerable component entirely if HEVC video playback is not required
Settings > Apps > Apps & features > HEVC Video Extensions > Uninstall
Restrict Media File Execution
windowsUse application control policies to block execution of media files from untrusted sources
🧯 If You Can't Patch
- Implement application whitelisting to prevent execution of unauthorized media players
- Educate users about risks of opening media files from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check Microsoft Store for HEVC Video Extensions updates or verify version in Apps & features settingsCheck Version:
Get-AppxPackage -Name Microsoft.HEVCVideoExtension* | Select-Object VersionVerify Fix Applied:
Confirm HEVC Video Extensions shows no available updates in Microsoft Store📡 Detection & Monitoring
Log Indicators:
- Unexpected process creation from media player applications
- HEVC Video Extensions crash events in Application logs
Network Indicators:
- Outbound connections from media player processes to unexpected destinations
SIEM Query:
Process Creation where (Image contains 'video' OR ParentImage contains 'video') AND CommandLine contains '.hevc' OR '.mp4' OR '.mov'