Windows 11 KB5127936 Fixes Always ON VPN Issues Caused by September 2026 KB5124008 Patch

Microsoft has finally fixed the Always On VPN connection issue triggered by Windows 11’s September security update. The problem affected devices using automatic VPN protocol selection or fallback, leaving connections stuck on Connecting. Now, the KB5127936 preview update resolves the issue for Windows 11 versions 25H2 and 26H2. Let’s not forget that the same update also fixed the Remote Desktop error 0xC000000D.

Windows 11 KB5124008 triggered frustrating VPN failures

The problem first surfaced after Microsoft released the September 2026 Patch Tuesday update, KB5124008. As previously reported, Windows 11 KB5124008 was breaking Always On VPN connections, affecting users struggled to establish VPN connections to corporate networks.

The issue became especially frustrating when an initial connection attempt failed. Subsequent attempts could remain stuck in the Connecting state or fail entirely, sometimes displaying the error, “The specified port is already in use.”

Microsoft initially marked the issue as resolved through October updates. However, the company later admitted that KB5127648 had not actually fixed the VPN bug. Administrators were advised to configure affected profiles to use either SSTP or IKEv2 instead of automatic protocol selection.

KB5127936 finally resolves the VPN issue

Microsoft has now confirmed the fix in the release notes for KB5127936, released last week. The update targets Windows 11 versions 25H2 and 26H2, with OS builds 26200.9818 and 26300.9818, respectively.

The update is an optional preview release, available through Windows Update under Settings > Windows Update > Advanced options > Optional updates. Organizations can also obtain the standalone packages through the Microsoft Update Catalog.

Meanwhile, Microsoft’s workaround remains relevant for systems that have not received the fix. Administrators can select a single tunneling protocol based on their network and security requirements. Last but not least, the KB5127936 preview has also resolved the Smart App Control bug that was triggered by the October 2026 KB5127648 security update.