Updates KB5009543, KB5009566 Crash L2TP VPN Connection on Windows

This guide provides a clear overview of windows update cause vpn error, including the main concepts, practical steps, and common questions. Use it to understand the topic, compare the available options, and make a more informed decision.

Immediately after installing the updates KB5009543 and KB5009566, many users reported that their computer crashed L2TP VPN connection when trying to connect using Windows VPN.

When trying to connect to a VPN device, the user gets the error message: "Can't connect to VPN. The L2TP connection attempt failed because the security layer encountered a processing error during initial negotiations with the remote computer", like you Seen in the photo below:

The Event Log also records an error code of 789, indicating a failed VPN connection:

This bug doesn't seem to affect all VPN devices and seems to only affect users who use the built-in Windows VPN to connect.

The fix at the moment is to remove the KB5009566 and KB5009543 updates. Once removed, the L2TP VPN connection will be restored as soon as the machine reboots.

Windows users can remove the KB5009566 and KB5009543 updates by accessing the Command Prompt in Administrator mode and then running the following commands:

- Windows 10: wusa /uninstall /kb:5009543 - Windows 11: wusa /uninstall /kb:5009566

Besides, you can also refer to how to uninstall Windows 11 update in the following article (also applicable to Windows 10): How to Uninstall a Windows 11 Update

Note: When you remove the KB5009566 and KB5009543 updates, you will also remove the bug fixes and vulnerability patches that are packaged by Microsoft. Therefore, you should only delete the update if you feel it is necessary.

Conclusion

Understanding Windows Update Cause VPN Error makes it easier to compare options, avoid common mistakes, and apply the information in this guide more effectively. Review the relevant requirements before making changes or choosing a solution.