CVE-2023-28220
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on systems running vulnerable Layer 2 Tunneling Protocol (L2TP) implementations. Attackers can exploit this without authentication by sending specially crafted packets to vulnerable systems. This affects Windows systems with L2TP services enabled.
💻 Affected Systems
- Microsoft Windows
📦 What is this software?
Windows 10 1507 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 20h2 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 11 21h2 by Microsoft
Windows 11 22h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with SYSTEM/root privileges, enabling attackers to install malware, steal data, pivot to other systems, or create persistent backdoors.
Likely Case
Remote code execution leading to system compromise, data exfiltration, or ransomware deployment on vulnerable systems.
If Mitigated
Limited impact due to network segmentation, proper patching, and disabled vulnerable services.
🎯 Exploit Status
Microsoft has confirmed exploitation in the wild. The vulnerability requires no authentication and has low attack complexity.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: April 2023 security updates
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-28220
Restart Required: Yes
Instructions:
1. Apply April 2023 Windows security updates. 2. Restart affected systems. 3. Verify patch installation via Windows Update history.
🔧 Temporary Workarounds
Disable L2TP Services
windowsDisable Layer 2 Tunneling Protocol services if not required
netsh interface set interface "Remote Access" admin=disable
sc config RemoteAccess start= disabled
sc stop RemoteAccess
Block L2TP Ports
windowsBlock UDP ports 1701 and 500 at network perimeter
netsh advfirewall firewall add rule name="Block L2TP" dir=in action=block protocol=UDP localport=1701,500
🧯 If You Can't Patch
- Disable L2TP VPN services on all vulnerable systems
- Implement strict network segmentation to isolate systems with L2TP enabled
🔍 How to Verify
Check if Vulnerable:
Check if L2TP services are running: sc query RemoteAccess | findstr RUNNINGCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify April 2023 security updates are installed: wmic qfe list | findstr "KB5025221 KB5025239 KB5025224"📡 Detection & Monitoring
Log Indicators:
- Event ID 4688 with suspicious process creation
- Unexpected L2TP connection attempts in firewall logs
- Windows Security logs showing exploitation attempts
Network Indicators:
- Unusual UDP traffic on port 1701 or 500
- Malformed L2TP packets
- Traffic from unexpected sources to L2TP services
SIEM Query:
source="windows" AND (event_id=4688 OR event_id=4625) AND (process_name="cmd.exe" OR process_name="powershell.exe") AND user="SYSTEM"