CVE-2025-24056
📋 TL;DR
A heap-based buffer overflow vulnerability in Windows Telephony Server allows remote attackers to execute arbitrary code without authentication. This affects Windows systems running the vulnerable Telephony Server component. Attackers can exploit this over a network to potentially take full control of affected systems.
💻 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 22h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 24h2 by Microsoft
Windows 11 24h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise leading to data theft, ransomware deployment, lateral movement within the network, and persistent backdoor installation.
Likely Case
Remote code execution leading to system compromise, credential harvesting, and initial access for further attacks.
If Mitigated
Limited impact with proper network segmentation and endpoint protection, potentially resulting in service disruption rather than full compromise.
🎯 Exploit Status
Network-based exploitation without authentication. Attack complexity may vary based on specific conditions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update for specific KB number
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-24056
Restart Required: Yes
Instructions:
1. Apply the latest Windows security update from Microsoft. 2. Restart affected systems. 3. Verify the patch is installed successfully.
🔧 Temporary Workarounds
Disable Telephony Server Service
WindowsDisable the vulnerable Telephony Server service if not required for business operations
sc stop TapiSrv
sc config TapiSrv start= disabled
Network Segmentation
WindowsRestrict network access to Telephony Server ports using firewall rules
New-NetFirewallRule -DisplayName "Block Telephony Server" -Direction Inbound -Protocol TCP -LocalPort 5060,5061 -Action Block
🧯 If You Can't Patch
- Implement strict network segmentation to isolate vulnerable systems
- Deploy endpoint detection and response (EDR) solutions with behavioral monitoring
🔍 How to Verify
Check if Vulnerable:
Check if Telephony Server service is running and if system has unpatched Windows versionCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify Windows Update history contains the relevant security patch and Telephony Server service is either patched or disabled📡 Detection & Monitoring
Log Indicators:
- Unusual Telephony Server service restarts
- Failed authentication attempts to Telephony Server
- Process creation from Telephony Server context
Network Indicators:
- Unusual network traffic to Telephony Server ports (typically 5060/5061)
- Suspicious RPC calls to Telephony Server
SIEM Query:
EventID=4688 AND NewProcessName="*\TapiSrv.exe" AND CommandLine CONTAINS "suspicious"