Microsoft says a security update for Windows 11 released this month may prevent some users from switching on a built-in protection feature. The company reported that the ability to enable Smart App Control can become unavailable after the KB5127648 update is installed. Smart App Control is a Windows 11 security feature that draws on Microsoft's app intelligence services and code integrity functions. It works alongside Microsoft Defender and SmartScreen to block potentially harmful apps or binaries.
The problem affects devices running Windows 11, version 24H2 and later. On those machines, the option to turn on Smart App Control inside the Windows Security app may appear grayed out, leaving users unable to toggle it. Microsoft said the issue surfaces when Smart App Control has been turned off. Devices where the feature is already active are not affected and remain protected, according to the company.
Microsoft outlined the problem in an update to its KB5127648 advisory. A permanent fix is not yet available, so the company provided temporary workarounds aimed at IT administrators who manage devices in enterprise settings. Administrators can either modify the registry or install a group policy to restore the ability to switch the feature on.
The registry workaround involves running two commands at a command prompt that add values under a FeatureManagement Overrides key, then restarting the device. Alternatively, IT admins can install and configure two Group Policies to turn on Smart App Control and to make sure logging is enabled for troubleshooting. Both policies are located under Computer Configuration, then Administrative Templates, and then the applicable Group Policy name for Windows 11, version 24H2 or 25H2. After installing them, admins must set both settings to Enabled and restart the affected devices.
The Smart App Control disclosure comes during a busy stretch of Windows update problems. Microsoft also confirmed this week that recent Windows updates cause Remote Desktop failures for non-admin users when the Administrator protection security feature is enabled. The company additionally resolved a known issue that triggered Always On VPN connection problems after the September 2026 security updates were installed.
Separately, on Tuesday, Microsoft addressed a bug that caused black screens, desktop loading issues and Explorer crashes after users installed Windows 11 updates released since August.
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