Microsoft's September Updates May Break Always On VPN Connections
Microsoft has confirmed that its upcoming September security updates for Windows 11 may cause Always On VPN connections to fail. The company issued an alert to IT administrators stating that the issue will occur when the September cumulative update is installed.
Affected systems may experience problems connecting to enterprise networks via Always On VPN, with the connection remaining in a 'Connecting' state or causing repeated retry attempts that are unsuccessful. Error messages such as 'The specified port is already in use' may also appear on later attempts.
The issue affects three Windows 11 releases: version 26H1 after installing KB5124012, version 25H2 after installing KB5124008, and version 24H2 after installing KB5124008. The problem occurs when the VPN is configured to attempt another connection method if the first one fails, such as with automatic protocol selection using IKEv2 and SSTP.
Microsoft recommends that IT administrators move affected profiles away from automatic protocol selection until a permanent solution is released. In the meantime, they can set the tunneling option to use a single protocol instead of automatically selecting it.