VPN affected by Windows updates

Question

Hello, I have a huge problem. We have a FortiGate firewall and connect remotely to our network with the Forticlient VPN. Fortigate support indicates that when attempting to connect the certificate is not accessed. The client receives an error "Unable to establish the VPN connection. The VPN server may be unreachable. (-5)". I realized that there were updates previous day and uninstalled KB5003637 and KB5003254. The VPN will work when these are not installed. I did the same on 6 other systems to prove my theory. Fortigate states that their setup is not the cause and now left me hanging. Does anyone have any advice or has come across this? How do I make Microsoft aware? Thank you

Answer 1

Hi,

Thanks for posting in Q&A platform.

Please kindly note that Forticlient VPN is a third-party VPN client which we're not familiar with. From windows side, to narrow down whether the issue is related to these 2 patches, I would suggest you login to the problematic device and uninstall KB5003637 firstly to see if the issue still existed. If not, then please uninstall KB5003254 to see if the issue was caused by this patch.

Then we would suggest you uninstall the impacted patch temporarily and wait for the next monthly update patch to see whether the issue still occur.

In addition, the Feedback Hub app lets you tell Microsoft about any problems you run in to while using Windows 10. You can report this issue to Microsoft directly with the Feedback Hub app.

For more information on using the app, click here:

Send feedback to Microsoft with the Feedback Hub app

If this issue is urgent, I would also suggest you contact Microsoft Customer Support and Services where more in-depth investigation can be done so that you would get a more satisfying explanation and solution to this issue.

You may find phone number for your region accordingly from the link below:

https://support.microsoft.com/en-us/gp/customer-service-phone-numbers

Best Regards,
Sunny

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Answer 2

Hi, I followed your suggestions but no response from Microsoft as of yet. It appears to be the KB5003637 update. Still working with Fortigate to see if they can resolve. Thanks

Answer 3

Update on this. We were using port 995 for the VPN. Changed it to another port number and it worked. The windows update KB5003637 was blocking this port apparently. Thanks