CVE-2021-1644
📋 TL;DR
CVE-2021-1644 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. Successful exploitation could give attackers control over the affected system.
💻 Affected Systems
- Microsoft HEVC Video Extensions
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining SYSTEM-level privileges, enabling data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Limited user-level code execution leading to credential harvesting, lateral movement within the network, or installation of additional malware.
If Mitigated
No impact if patched or if HEVC extensions are not installed; limited impact if user runs with restricted privileges and application sandboxing is effective.
🎯 Exploit Status
Requires user interaction to open malicious media file; exploitation details not publicly disclosed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: HEVC Video Extensions version from January 2021 or later
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-1644
Restart Required: No
Instructions:
1. Open Microsoft Store. 2. Search for 'HEVC Video Extensions'. 3. Click 'Get Updates' or check for updates. 4. Install available updates. 5. Alternatively, update through Windows Update if extensions were installed via system.
🔧 Temporary Workarounds
Uninstall HEVC Video Extensions
windowsRemove the vulnerable component entirely if not needed for business operations
Get-AppxPackage *HEVC* | Remove-AppxPackage
Restrict media file execution
windowsUse application control policies to block execution of HEVC files from untrusted sources
🧯 If You Can't Patch
- Disable automatic opening of media files in email clients and web browsers
- Implement network segmentation to limit lateral movement if exploitation occurs
🔍 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 January 2021 or later: Get-AppxPackage *HEVC* | Select Version📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing crashes in HEVC extensions (Event ID 1000)
- Process creation from media player applications with suspicious command lines
Network Indicators:
- Outbound connections from media player processes to suspicious IPs
- DNS queries for known C2 domains from media-related processes
SIEM Query:
source="Windows Security" AND (event_id=4688 OR event_id=4689) AND process_name="*HEVC*" OR parent_process="*media*"