CVE-2024-38140
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on affected Windows systems by sending specially crafted packets to the Reliable Multicast Transport driver. It affects Windows systems with the RMCAST driver enabled, primarily servers using multicast protocols. Attackers can gain SYSTEM-level privileges without user interaction.
💻 Affected Systems
- Windows Server
- Windows Client
📦 What is this software?
Windows 10 1507 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 11 21h2 by Microsoft
Windows 11 22h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 24h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with SYSTEM privileges, enabling data theft, ransomware deployment, lateral movement, and persistent backdoors.
Likely Case
Initial foothold for attackers leading to privilege escalation, credential harvesting, and network reconnaissance.
If Mitigated
Limited impact due to network segmentation, host-based firewalls blocking multicast traffic, and proper patch management.
🎯 Exploit Status
Exploitation requires network access to the vulnerable service. No authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: July 2024 security updates (KB5040442 for Windows 11, KB5040437 for Windows 10, etc.)
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-38140
Restart Required: Yes
Instructions:
1. Apply July 2024 Windows security updates via Windows Update. 2. For enterprise: Deploy patches through WSUS, SCCM, or Intune. 3. Restart systems after patch installation.
🔧 Temporary Workarounds
Disable RMCAST driver
windowsDisables the vulnerable driver if not needed for multicast functionality.
sc stop rmcast
sc config rmcast start= disabled
Block multicast traffic
allConfigure firewalls to block multicast traffic (224.0.0.0/4) to vulnerable systems.
🧯 If You Can't Patch
- Segment networks to restrict multicast traffic to trusted systems only.
- Implement host-based firewalls to block incoming multicast packets on vulnerable systems.
🔍 How to Verify
Check if Vulnerable:
Check if RMCAST driver is running: 'sc query rmcast' shows SERVICE_RUNNING. Check Windows version with 'winver' and compare to affected versions.Check Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify July 2024 security updates are installed via 'wmic qfe list' or Settings > Windows Update > Update history. Confirm RMCAST driver version is updated.📡 Detection & Monitoring
Log Indicators:
- Event ID 7036 for RMCAST service stopping/crashing
- Unexpected SYSTEM-level process creation
- Network connections to multicast addresses
Network Indicators:
- Unusual multicast traffic patterns
- Exploit-specific packet signatures (if known)
- Traffic to 224.0.0.0/4 range
SIEM Query:
source="windows" event_id=7036 AND service_name="rmcast" OR process_name="rmcast.sys"