In a service alert seen by BleepingComputer and shared by Microsoft MVP Susan Bradley, the company said customers who have applied the September 2026 Windows 11 security updates may encounter connectivity problems when their devices try to reach the corporate network via Always On VPN.
Always On VPN is Microsoft’s modern remote‑access solution that replaces the older DirectAccess technology and supports domain‑joined, non‑domain‑joined and Microsoft Entra ID‑joined devices on Windows 10, Windows 11 and Windows Server.
The alert explains that the issue typically appears when the VPN profile is set to automatic protocol selection – a fallback mechanism that switches between IKEv2 and SSTP if the first attempt fails. Under the faulty update, affected connections can remain in a “Connecting” state, repeatedly retry without success, or display the error “The specified port is already in use.”
Microsoft said it is still working on a permanent fix, but recommends a temporary mitigation: administrators should edit the Always On VPN profile to use a single tunneling protocol – either SSTP only or IKEv2 only – based on their environment and security requirements.
The September 2026 cumulative updates have already triggered a series of other problems for both home and enterprise users, including Hyper‑V crashes, Remote Desktop Services failures, USB audio glitches, a login issue that blocks domain credentials, and a bug that can stop the built‑in File History backup feature.
Enterprises are advised to review their VPN configurations promptly, apply the suggested protocol‑specific setting, and monitor Microsoft’s forthcoming patches for a definitive resolution.