Microsoft fixes VPN issues caused by September Windows updates
Microsoft's October updates fix Always On VPN failures on Windows 11 caused by September 2026 patches.
Microsoft fixed an Always On VPN failure introduced by the September 2026 Windows 11 security updates. On Windows 11 24H2 and later, automatic selection or fallback between IKEv2 and SSTP could leave connections stuck in Connecting or return “The specified port is already in use.” Cumulative updates KB5127648 and KB5127646 resolve it; administrators who cannot patch immediately can force a single protocol, SSTP or IKEv2. Microsoft also noted separate Remote Desktop connection problems for non-admin users when Administrator protection is enabled.
- September 2026 Windows 11 updates broke Always On VPN fallback.
- Connections could stay Connecting or report the port already in use.
- KB5127648 and KB5127646 fix affected Windows 11 24H2 and later systems.
- A workaround is forcing SSTP-only or IKEv2-only profiles.
Full article387 words · extracted from bleepingcomputer.com · click to collapse
Microsoft has resolved a known issue that caused Always On VPN connection issues after installing the September 2026 Windows 11 security updates.
The Always On VPN remote access solution replaced the legacy DirectAccess technology and works with domain-joined, non-domain-joined, and Microsoft Entra ID–joined Windows 10, Windows 11, and Windows Server devices.
Always On VPN runs in the background and automatically establishes a secure tunnel back to the corporate network whenever a device connects to the internet.
As Microsoft first acknowledged in a service alert sent to IT administrators in late September, the bug triggered Always On VPN failures if the initial connection fails (e.g., when using automatic protocol selection with IKEv2 and SSTP) on up-to-date systems running Windows 11 24H2 and later.
On Tuesday, the company released the KB5127648 and KB5127646 cumulative updates that address this known issue on all affected systems.
"When automatic protocol selection or protocol fallback was configured, affected VPN connections could remain stuck in a Connecting state or fail to connect after an initial connection attempt failed," it said. "In some cases, subsequent connection attempts could display the error, 'The specified port is already in use.'"
Microsoft has also shared a temporary fix for customers who can't immediately install the October 2026 Patch Tuesday update, which requires them to choose one of 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," Microsoft said. "Organizations should select the protocol based on their environment, security, and deployment requirements."
Last month, it released emergency updates to fix Remote Desktop Services failures, Hyper-V issues, and USB audio problems affecting home and enterprise Windows users, which were also triggered by the September 2026 updates.
This week, it also confirmed that non-admin users may have issues connecting to devices via Remote Desktop after installing recent Windows updates if the "Administrator protection" security feature is enabled.
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.