KB5009543 and KB5009566 updates are breaking VPN connections in Windows

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Updates for Windows are supposed to fix problems, boost security and add new features, but all too often they cause problems of their own. This month's Patch Tuesday updates for Windows 10 and Windows 11 are no different in this regard.

Earlier this week, Microsoft released KB5009543 for Windows 10 and KB5009566 for Windows 11. Users who have installed either of these updates are reporting issues with L2TP VPN connections.

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It is only Windows' built-in VPN client that appears to be broken, with third -party tools remaining unimpaired. According to reports, there are not problems with all VPN devices, but Reddit users are complaining of issues with connections to SonicWall and WatchGuard Firewalls.

People whose systems are affected by the problem have been alerted to the fact by the appearance of an error message reading:

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.

At the moment, there is no official fix or workaround for the VPN issues, leaving affected users with just one option -- uninstall the offending updates. This can achieved from an elevated Command Prompt using the following commands.

For Windows 10:

wusa /uninstall /kb:5009543

For Windows 11:

wusa /uninstall /kb:5009566

Image credit: spatuletail / Shutterstock

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