OpenVPN Driver Vulnerabilities Crashing Windows?

Yes, vulnerable or buggy OpenVPN TAP and Wintun drivers can crash Windows, typically causing a Blue Screen of Death (BSOD) during installation, connection, or disconnection. This article explains why these crashes happen, how to identify the faulty driver, and the steps to fix or prevent them.

Background: How OpenVPN Drivers Work on Windows

OpenVPN on Windows relies on a virtual network adapter to route traffic. Two main drivers are used:

• TAP-Windows – the older, widely used driver that creates a virtual Ethernet adapter. It has been the default for many years.
• Wintun – a newer, lighter driver designed for WireGuard and newer OpenVPN versions. It is faster but has its own update cycle.

These drivers run in kernel mode, meaning they have high-level access to system resources. A bug or vulnerability in a kernel driver can cause memory corruption, leading to a system crash (BSOD) or, in worse cases, privilege escalation for an attacker.

Known Vulnerabilities and Crash Triggers

Several security advisories have highlighted flaws in OpenVPN’s Windows drivers:

• CVE-2022-33681 – a privilege escalation vulnerability in the TAP driver that could allow a local attacker to gain SYSTEM privileges. While not directly a crash, exploitation could destabilize the system.
• Driver signature issues – older versions of the TAP driver may lack proper Microsoft signature, causing Windows to block them or crash on load.
• Memory corruption bugs – certain malformed network packets can trigger buffer overflows in the driver, leading to a BSOD.

Common crash triggers include:

• Updating Windows while an old OpenVPN driver is still installed.
• Using a VPN client that bundles an outdated or patched version of the driver.
• Connecting or disconnecting rapidly, causing race conditions in the driver.
• Running multiple VPN clients simultaneously that both try to use the same TAP adapter.

How to Identify the Faulty Driver

When Windows crashes, it creates a minidump file. You can analyze it to see if the crash is driver-related:

1. Open Event Viewer (Win + R, type eventvwr.msc).
2. Go to Windows Logs > System and look for critical errors with source BugCheck.
3. Note the bug check code (e.g., 0x000000D1 – DRIVER_IRQL_NOT_LESS_OR_EQUAL).
4. Use a tool like WinDbg (from Microsoft Store) to open the minidump file (C:\Windows\Minidump) and run !analyze -v. It will often list the driver name.

Common driver names that appear: tap0901.sys, tap-windows6.sys, wintun.sys.

Fixing Crashes Caused by OpenVPN Drivers

If you suspect the OpenVPN driver is causing crashes, follow these steps in order:

1. Update OpenVPN – Install the latest version from the official OpenVPN community or your VPN provider. Newer versions include patched drivers.
2. Reinstall the driver – Go to Device Manager, expand Network adapters, right-click the TAP or Wintun adapter, and select Uninstall device. Then restart and reinstall OpenVPN.
3. Switch drivers – In OpenVPN GUI, go to Settings > Advanced and select Wintun instead of TAP (or vice versa). This can bypass a buggy driver.
4. Remove old driver remnants – Use the tapinstall.exe utility (in the OpenVPN bin folder) to remove old TAP adapters: tapinstall.exe remove tap0901.
5. Check for Windows updates – Sometimes a Windows update fixes a compatibility issue with the driver.
6. Run a clean boot – Disable all non-Microsoft services and startup items to see if another software is conflicting.

Preventing Future Crashes

To minimize the risk of driver-related BSODs:

• Always keep OpenVPN and your VPN client updated.
• Uninstall old VPN software completely before installing a new one.
• Use the built-in Windows VPN client (IKEv2 or SSTP) if you don’t need OpenVPN-specific features.
• If you use multiple VPN tools, ensure they don’t share the same TAP adapter.
• Regularly check the OpenVPN community forums for known driver issues.

Comparisons: TAP vs Wintun Driver Stability

Both drivers have had bugs, but Wintun is generally considered more stable on modern Windows 10/11 because it is actively maintained and has a smaller codebase. TAP is older and has more legacy issues, but some older VPN configurations still require it. If you experience crashes with one, switching to the other often resolves the problem.

Frequently Asked Questions

Can a vulnerable OpenVPN driver be exploited remotely?

Most known vulnerabilities require local access to the system. Remote exploitation is rare but possible if combined with another flaw. Keeping the driver updated is the best defense.

How do I know if my OpenVPN driver is outdated?

In the OpenVPN GUI, go to Help > About to see the version. Compare it with the latest release on the official OpenVPN site. Also, check the driver file version in Device Manager > Driver tab.

Will uninstalling OpenVPN remove the driver?

Not always. The TAP driver may remain installed. Use the tapinstall.exe remove command or manually delete the driver from Device Manager.

Can I use OpenVPN without installing a driver?

No, OpenVPN requires a virtual network adapter driver to create the VPN tunnel. However, you can use the built-in Windows VPN client instead.

My VPN provider uses a custom client. Does it use OpenVPN drivers?

Many providers bundle OpenVPN and its drivers. If you see TAP or Wintun in Device Manager, yes. Check your provider’s documentation for specifics.

What should I do if the BSOD occurs during boot?

Boot into Safe Mode (Shift + Restart > Troubleshoot > Advanced > Startup Settings). Then uninstall the OpenVPN driver or use System Restore to a point before the issue.

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