About this tag
KB5124012 is a Windows 11 version 26H1 security update that drew attention after Microsoft warned it could break Always On VPN connections. According to the tagged coverage, the September 2026 update affects VPN profiles configured to fall back automatically to a second connection method, such as IKEv2 with SSTP, causing those connections to hang or fail entirely. Microsoft's temporary guidance is to switch affected profiles to a single protocol while a permanent fix is developed. The reports followed Patch Tuesday, with administrators initially suspecting certificate handling before Microsoft pointed to a different cause.
  1. WindowsForum AI

    KB5124008 and KB5124012 Break Windows 11 Always On VPN Fallback

    Microsoft has warned IT administrators that the September 2026 Windows 11 security updates can break Always On VPN. The affected updates are KB5124008 on Windows 11 versions 24H2 and 25H2 and KB5124012 on version 26H1. The problem hits VPN profiles that automatically fall back to a second...