CVE-2021-3613
📋 TL;DR
CVE-2021-3613 is a local privilege escalation vulnerability in OpenVPN Connect for Windows that allows local users to load arbitrary dynamic libraries via an OpenSSL configuration file. This enables attackers to execute arbitrary code with the same privileges as the OpenVPN process. Only users running OpenVPN Connect 3.2.0 through 3.3.0 on Windows are affected.
💻 Affected Systems
- OpenVPN Connect for Windows
📦 What is this software?
Connect by Openvpn
⚠️ Risk & Real-World Impact
Worst Case
Local attacker gains full control of the OpenVPN process, potentially leading to system compromise, credential theft, or network traffic interception.
Likely Case
Local user with limited privileges escalates to the OpenVPN process level, enabling them to manipulate VPN connections or access protected resources.
If Mitigated
With proper access controls and patching, impact is limited to denial of service at most.
🎯 Exploit Status
Exploitation requires local access to the system. The vulnerability is well-documented and relatively simple to exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: OpenVPN Connect 3.3.1 and later
Vendor Advisory: https://openvpn.net/vpn-server-resources/openvpn-connect-for-windows-change-log/
Restart Required: Yes
Instructions:
1. Download OpenVPN Connect 3.3.1 or later from the official OpenVPN website. 2. Uninstall the current vulnerable version. 3. Install the updated version. 4. Restart the system to ensure all processes use the patched version.
🔧 Temporary Workarounds
Restrict OpenSSL configuration file access
windowsSet strict file permissions to prevent unauthorized users from creating or modifying OpenSSL configuration files in directories accessible by OpenVPN Connect.
icacls "C:\Program Files\OpenVPN Connect\" /deny Users:(OI)(CI)W
Remove vulnerable versions
windowsUninstall OpenVPN Connect versions 3.2.0 through 3.3.0 if patching is not immediately possible.
appwiz.cpl
🧯 If You Can't Patch
- Implement strict access controls to limit local user privileges on systems running OpenVPN Connect.
- Monitor for suspicious file creation/modification in OpenVPN Connect directories and OpenSSL configuration file usage.
🔍 How to Verify
Check if Vulnerable:
Check OpenVPN Connect version in Windows Programs and Features or via 'OpenVPN Connect' > 'About' in the application.Check Version:
wmic product where name="OpenVPN Connect" get versionVerify Fix Applied:
Verify installed version is 3.3.1 or later and check that OpenSSL configuration file loading is properly restricted.📡 Detection & Monitoring
Log Indicators:
- Unexpected OpenSSL configuration file loading
- OpenVPN process spawning unexpected child processes
- File creation/modification in OpenVPN directories
Network Indicators:
- Unusual VPN connection patterns
- Unexpected outbound connections from OpenVPN process
SIEM Query:
EventID=4688 AND ProcessName="OpenVPNConnect.exe" AND ParentProcessName NOT IN ("explorer.exe", "services.exe")