CVE-2024-43518
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on Windows systems running the Telephony Server service. Attackers can exploit this heap-based buffer overflow (CWE-122) to gain SYSTEM privileges. All Windows systems with the vulnerable Telephony Server component are affected.
💻 Affected Systems
- Windows Telephony Server
📦 What is this software?
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 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 lateral movement, data exfiltration, and persistent backdoor installation.
Likely Case
Remote code execution leading to malware deployment, ransomware infection, or credential theft from the compromised system.
If Mitigated
Limited impact due to network segmentation, proper patching, and restricted service permissions preventing successful exploitation.
🎯 Exploit Status
Exploitation requires sending specially crafted packets to the Telephony Server service. No authentication is needed if the service is exposed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply the latest Windows security updates from Microsoft's May 2024 Patch Tuesday or later
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-43518
Restart Required: Yes
Instructions:
1. Open Windows Update settings. 2. Click 'Check for updates'. 3. Install all available security updates. 4. Restart the system when prompted.
🔧 Temporary Workarounds
Disable Telephony Server Service
windowsStop and disable the Telephony Server service if not required for business operations
sc stop Tapisrv
sc config Tapisrv start= disabled
Block Network Access to Telephony Server
windowsUse Windows Firewall to block inbound connections to Telephony Server ports
netsh advfirewall firewall add rule name="Block Telephony Server" dir=in action=block protocol=TCP localport=3372,3373
🧯 If You Can't Patch
- Implement strict network segmentation to isolate systems running Telephony Server
- Deploy endpoint detection and response (EDR) solutions to monitor for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check if Telephony Server service (Tapisrv) is running and if system has not applied May 2024 Windows security updatesCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify Windows Update history shows installation of KB5037768 (May 2024) or later security updates📡 Detection & Monitoring
Log Indicators:
- Event ID 4688: New process creation from Tapisrv.exe
- Event ID 4624: Failed logon attempts from SYSTEM context
- Unusual network connections from Telephony Server port 3372/3373
Network Indicators:
- Unusual traffic to TCP ports 3372 or 3373
- Malformed packets targeting Telephony Server service
SIEM Query:
source="windows" AND (event_id=4688 AND process_name="Tapisrv.exe") OR (destination_port=3372 OR destination_port=3373)