NetExtender error: SSL error happened, your OS not support connecting to the server. Please make sure the server has valid certificate setup.

This article details a work around regarding SSLVPN issues due to Windows update in October 2022.

Windows 10 update KB5018410 breaks currently functional SSL VPN connections.

Environment

Clients: Windows 10 Professional. SSL VPN connections using built-in Windows VPN client.

Server: Windows 2008 R2 using a self-signed certificate.

Resolution 

The below resolution is for customers using SonicOS 7.X firmware and  SonicOS 6.5 firmware

The only solution that works, at this time, is to manually Uninstall KB5018410 and pause updates to prevent reinstallation.

STEP 1 - Uninstalling the patch:

1. Go to Control Panel | Programs | Programs and Features and click on View installed updates.

2. Find the update that contains the KB5018410 patch, click on it and then press Uninstall.

STEP 2 - Pausing windows updates:

1. Go to the start menu and search for Advanced Windows Update option

2. Enable Pause updates

NOTE: If you are using Windows 10 Professional, Enterprise, or higher you may not see this option available. To enable the option:

3. Restart the device.