Microsoft has fixed a known Windows 11 issue that prevented some users from activating Smart App Control after installing the October 2026 KB5127648 security update. On affected devices, the option in the Windows Security app appeared grayed out when the feature had previously been disabled.
Smart App Control uses Microsoft’s code integrity and app intelligence services alongside SmartScreen and Microsoft Defender to block potentially harmful applications and binaries. Devices where the feature was already enabled were not affected and continued to be protected.
The company confirmed that the issue was resolved by updates released on October 28, 2026, including the KB5127936 preview update, and later releases. Microsoft recommends installing the latest security update because it includes the fix and other improvements.
For enterprise administrators who prefer not to deploy the preview update, Microsoft provided a temporary registry-based workaround. It requires running two registry commands with administrator privileges and restarting affected devices. Administrators can also use specific Group Policy packages for Windows 11 versions 24H2, 25H2, and 26H2 to enable Smart App Control and logging, followed by a restart.
The KB5127936 preview update also addresses Remote Desktop failures associated with the Administrator protection feature and resolves Always On VPN problems linked to the September 2026 cumulative updates.
Sources: BleepingComputer.