Microsoft released the latest update of Windows 10 and Windows 11 last week. The update, however, contained a rather important bug, which blocked VPN connections for PCs with Windows 10, returning users an error message whenever they tried to connect to a private network.
The problem is present in version KB5009543 of Windows 10, published on the occasion of the Microsoft Patch Tuesday of January: given the importance of the update of the Patch Tuesday, which solved almost 100 security vulnerabilities, many users have
In particular, the error message presented by Windows 10 says “Can’t connect to VPN. The L2TP connection attempt failed because the security level encountered a processing error during connections started with the remote computer.” Microsoft explained that the problem concerns only VPNs with L2TP protocol, but at the moment they are numerous and scattered around the world.
Microsoft has confirmed the problem over the past few hours, saying “After installing the KB5009543 version of Windows 10, IP Security connections (IPSEC) with a Vendor ID may fail. The problem may be affected by L2TP VPN connections, which use Layer 2 Tunneling Protocol, or IPSEC IKE connections, or IP security Internet Key Exchange.”
At the same time, Microsoft has released a fix for the problem via an update Out-Of-Band for Windows 10. Among the notes of the update, Redmond’s home explained that “Microsoft releases this Out-of-Band (OoB) update today, on January 17, 2022, for some versions of Windows. The update solves problems related to VPN connectivity, Windows Server Domain Controller restart and virtual machine boot problems.”