CVE-2025-27487
📋 TL;DR
A heap-based buffer overflow vulnerability in Microsoft Remote Desktop Client allows authenticated attackers to execute arbitrary code remotely by sending specially crafted network packets. This affects users connecting to potentially malicious RDP servers or compromised legitimate servers. The vulnerability requires the attacker to have valid credentials for the RDP session.
💻 Affected Systems
- Microsoft Remote Desktop Client
📦 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 22h2 by Microsoft
Windows 11 22h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 24h2 by Microsoft
Windows App by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with remote code execution leading to data theft, ransomware deployment, or persistent backdoor installation on the client system.
Likely Case
Attacker gains control of the client system, potentially pivoting to internal networks, stealing credentials, or deploying malware.
If Mitigated
Limited impact due to network segmentation, application allowlisting, and proper credential management preventing exploitation.
🎯 Exploit Status
Requires attacker to control or compromise an RDP server that the victim connects to, plus valid authentication credentials for the session.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: To be specified in Microsoft's monthly security updates
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-27487
Restart Required: Yes
Instructions:
1. Open Windows Update settings
2. Check for updates
3. Install all available security updates
4. Restart the system when prompted
🔧 Temporary Workarounds
Disable RDP Client Connections
windowsPrevent use of Remote Desktop Client for connections to untrusted servers
Not applicable - configure via Group Policy or registry
Network Segmentation
allRestrict RDP client traffic to trusted internal servers only
🧯 If You Can't Patch
- Implement application control to restrict execution of unauthorized code on client systems
- Use network monitoring to detect anomalous RDP connections and block suspicious destinations
🔍 How to Verify
Check if Vulnerable:
Check Windows version and installed updates against Microsoft's security bulletinCheck Version:
winverVerify Fix Applied:
Verify the latest security updates are installed and version matches patched release📡 Detection & Monitoring
Log Indicators:
- Event ID 4625 (failed logon) followed by successful RDP connection
- Unusual process creation from mstsc.exe or related RDP processes
Network Indicators:
- RDP connections to unknown or suspicious external IP addresses
- Anomalous RDP packet patterns or sizes
SIEM Query:
source="windows-security" event_id=4625 logon_type=10 | join source="network-traffic" dest_port=3389