CVE-2020-25744
📋 TL;DR
This vulnerability in SaferVPN for Windows allows low-privileged users to create or overwrite arbitrary files by exploiting a symlink vulnerability in the Log directory. This could lead to denial of service (DoS) conditions or potentially more severe impacts through file manipulation. Only Windows users running vulnerable SaferVPN versions are affected.
💻 Affected Systems
- SaferVPN for Windows
📦 What is this software?
Safervpn by Safervpn
⚠️ Risk & Real-World Impact
Worst Case
An attacker could overwrite critical system files, potentially leading to system instability, data loss, or privilege escalation if combined with other vulnerabilities.
Likely Case
Local low-privileged users could cause DoS by overwriting important files or disrupt VPN functionality by manipulating configuration/log files.
If Mitigated
With proper user privilege separation and file permission controls, impact is limited to non-critical file manipulation within user context.
🎯 Exploit Status
Exploitation requires local access but is straightforward once access is obtained. Public proof-of-concept details available in referenced articles.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.0.3.3 and later
Vendor Advisory: Not publicly documented in vendor advisory, but referenced in security researcher publications.
Restart Required: Yes
Instructions:
1. Download SaferVPN version 5.0.3.3 or later from official sources. 2. Uninstall current vulnerable version. 3. Install updated version. 4. Restart system to ensure clean state.
🔧 Temporary Workarounds
Remove vulnerable symlink
windowsDelete or secure the vulnerable symbolic link in the SaferVPN Log directory
del /f /q "%LOCALAPPDATA%\SaferVPN\Log"
Restrict file permissions
windowsSet restrictive permissions on SaferVPN directories to prevent symlink creation
icacls "%LOCALAPPDATA%\SaferVPN" /deny Users:(OI)(CI)W
🧯 If You Can't Patch
- Implement strict user privilege separation to limit low-privileged user access
- Monitor and audit file creation/modification in SaferVPN directories
🔍 How to Verify
Check if Vulnerable:
Check SaferVPN version in Settings > About. If version is below 5.0.3.3, system is vulnerable.Check Version:
wmic product where name="SaferVPN" get versionVerify Fix Applied:
Verify SaferVPN version is 5.0.3.3 or higher and test symlink creation in %LOCALAPPDATA%\SaferVPN\Log directory.📡 Detection & Monitoring
Log Indicators:
- Unusual file creation/modification in SaferVPN directories
- Failed file access attempts to protected system locations
Network Indicators:
- None - this is a local file system vulnerability
SIEM Query:
EventID=4663 AND ObjectName LIKE "%SaferVPN%" AND Accesses="WriteData" OR "AppendData"