CVE-2025-25565
📋 TL;DR
SoftEther VPN 5.02.5187 contains a buffer overflow vulnerability in PtMakeCert and PtMakeCert2048 functions in Command.c. This allows attackers to execute arbitrary code by providing overly long input strings. The vulnerability affects users who run SoftEther VPN with command-line certificate generation capabilities.
💻 Affected Systems
- SoftEther VPN
📦 What is this software?
Vpn by Softether
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Local privilege escalation or denial of service affecting the VPN service availability.
If Mitigated
Limited impact due to the vendor's claim that users can only attack themselves via command-line input.
🎯 Exploit Status
Exploitation requires command-line access to the vulnerable functions. Public proof-of-concept demonstrates buffer overflow triggering.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not available
Vendor Advisory: Not available
Restart Required: No
Instructions:
No official patch available. Consider upgrading to latest version if available or implementing workarounds.
🔧 Temporary Workarounds
Restrict Command-Line Access
allLimit access to SoftEther VPN command-line interface to trusted administrators only.
Implement least privilege access controls
Use sudo/runas restrictions
Input Validation
allImplement input length validation for certificate generation parameters.
Modify Command.c to validate input lengths before processing
🧯 If You Can't Patch
- Disable command-line certificate generation features if not required
- Implement network segmentation to isolate SoftEther VPN servers
🔍 How to Verify
Check if Vulnerable:
Check SoftEther VPN version using 'vpncmd' command or version file. Version 5.02.5187 is vulnerable.Check Version:
vpncmd /client localhost /cmd AboutVerify Fix Applied:
Verify version is updated beyond 5.02.5187 or workarounds are implemented.📡 Detection & Monitoring
Log Indicators:
- Unusually long certificate generation requests
- Process crashes in SoftEther VPN service
Network Indicators:
- Abnormal traffic patterns from VPN servers
- Connection attempts to unusual ports
SIEM Query:
source="softether" AND (event="crash" OR command_length>1000)