Microsoft's release notes for KB5127936 say the update repairs Always On VPN connections broken by the September security update. The update is a Windows 11 preview dated October 28, 2026, and covers versions 26H2 and 25H2. Microsoft says the trouble hit setups using automatic protocol selection or fallback. Those connections could stay stuck on "Connecting" or fail after a first attempt did not work. Later attempts sometimes showed an error saying the port was already in use.
Protocol fallback means the VPN client tries one tunnel type first, then switches to another if that fails. Microsoft gives no cause for the failure, and it does not say how many devices were hit. Microsoft also lists a separate open problem. Since the September 8 security update, some USB Audio Class 1.0 devices may not start or may give no sound. Microsoft is working on a fix and gave no date.
A fix that ships only as a preview, after a September update broke VPN links, is a reason to test before trusting it. IT teams can check which VPN profiles use automatic protocol selection. They can also ask whether a small pilot group can try this preview first.