Microsoft: September Windows updates break Always On VPN connections

Summary

Microsoft has alerted IT administrators that its September 2026 security updates for Windows 11 may cause Always On VPN connections to fail. The issue occurs when the VPN is configured for automatic protocol selection and attempts to switch between IKEv2 and SSTP. A temporary workaround involves manually selecting a single protocol (SSTP or IKEv2) in the VPN profile.

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Microsoft: September Windows updates break Always On VPN connections By Sergiu Gatlan September 23, 2026 07:18 AM 0 Microsoft has notified IT administrators that users may experience Always On VPN connection issues after installing the September 2026 Windows 11 security updates. Always On VPN is a remote access solution that replaces the legacy DirectAccess technology and works with domain-joined, non-domain-joined, and Microsoft Entra ID–joined devices. It is available on Windows 10, Windows 11, and Windows Server, and it runs seamlessly in the background, establishing a secure tunnel back to the corporate network automatically whenever a device connects to the internet. Always On VPN also lets administrators define which apps and services can use the VPN connection, and it supports modern VPN protocols like IKEv2 and SSTP, plus multi-factor authentication (MFA) for better security. In a service alert seen by BleepingComputer and shared by Microsoft MVP Susan Bradley, Microsoft says that affected customers may experience issues when their systems attempt to connect to their organization's enterprise network via Always On VPN. "This issue can occur when the VPN is configured to automatically try another connection method if the initial connection fails (for example, when using automatic protocol selection with IKEv2 and SSTP)," Microsoft said. "Affected VPN connections might remain in a 'Connecting' state or repeatedly attempt to connect without succeeding. Subsequent connection attempts might also display the error: 'The specified port is already in use.'" Affected Versions Originating update Windows 11, version 26H1 KB5124012 Windows 11, version 25H2 KB5124008 Windows 11, version 24H2 KB5124008 While Microsoft is still working on a permanent solution, it shared a temporary fix for affected customers that requires them to choose one of the two VPN tunneling protocols to work around the issue. "IT administrators can mitigate this issue by changing the Always On VPN profile from automatic protocol selection to a single protocol, either SSTP only or IKEv2 only, depending on their environment and configuration," it said. "Organizations should select the protocol based on their environment, security, and deployment requirements." This month's cumulative updates have been linked to multiple other issues affecting both home and enterprise Windows users. One week ago, Microsoft released emergency updates to fix Hyper-V issues, Remote Desktop Services failures, and USB audio problems also triggered by the September 2026 updates. It also shared a temporary workaround for a separate issue that blocks some Windows 11 users from logging in with valid domain credentials and announced that it is working to address another bug that may cause the built-in File History backup feature in Windows to stop working. Build your security blueprint for AI-powered attacks Join Mikko Hyppönen and security leaders from the NFL, CHANEL, and Atlassian for a two-hour digital summit on what AI-speed attacks change, what defenders should stop doing, and how to validate, decide, fix, and re-validate at machine speed. Save your seat Related Articles: Microsoft: September updates break File History backup featureMicrosoft fixes bug behind ‘Defender Antivirus is turned off’ alertsMicrosoft shares workaround for Windows domain login issuesMicrosoft: September updates cause RDS failures on Windows ServerMicrosoft: September updates break audio on some Windows PCs

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