Microsoft: October Windows update may break Smart App Control

Microsoft says some users may have trouble turning on Smart App Control after this month's KB5127648 Windows 11 security update. On Windows 11, version 24H2 and later, the Windows Security option can be grayed out when the feature has been turned off. BleepingComputer's report by Sergiu Gatlan, published October 16, 2026, at 4:44 a.m., quotes the updated KB5127648 advisory.

This piece is for IT administrators on enterprise-managed Windows 11 versions 24H2, 25H2, and 26H2, and for users who had turned Smart App Control off before KB5127648. It covers the advisory, the registry commands, the two KB5074105 Group Policies set to Enabled, and the restart those steps require while a fix is still unavailable.

October Windows update may break Smart App: what actually changed

Microsoft updated the KB5127648 advisory for this month's Windows 11 security update. "After installing this update, some devices might be unable to turn on Smart App Control in the Windows Security app if it has been turned off. On affected devices, the option to turn on Smart App Control might be grayed out," Microsoft said. The same note states, "Devices where Smart App Control is already turned on are not affected and remain protected." Both sentences are in the KB5127648 advisory update.

Affected devices run Windows 11, version 24H2 and later, where Smart App Control cannot be toggled in the Windows Security app. A fix is not available yet. Temporary workarounds let IT administrators on enterprise-managed devices modify the registry or install a Group Policy, to restore the ability to turn Smart App Control on. The policies are KB5074105 261015_19222 Feature Preview and KB5074105 261015_19221 Feature Preview, for Windows 11 versions 24H2, 25H2, and 26H2. Both paths require a restart of the affected device.

October Windows update may break Smart App: how it works

Smart App Control is a Windows 11 security feature that uses Microsoft's app intelligence services and code integrity features. It works alongside Microsoft Defender and SmartScreen to block potentially harmful apps or binaries. KB5127648 leaves that protection in place when Smart App Control is already on. When the feature has been turned off, the Windows Security app grays out the option on some devices running Windows 11, version 24H2 and later, so the control cannot be switched on after KB5127648.

Type cmd in the Search box, select Run as Administrator, run both commands, and restart. First, reg add "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2883193997 /t REG_DWORD /d 1 /f. Second, reg add "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2850574478 /t REG_DWORD /d 1 /f. Admins can also install "Windows 11, versions 24H2, 25H2, and 26H2 - KB5074105 261015_19222 Feature Preview" and "Windows 11, versions 24H2, 25H2, and 26H2 - KB5074105 261015_19221 Feature Preview", found under Computer Configuration > Administrative Templates > {Group Policy name} > Windows 11, version 24H2, 25H2. Set both to Enabled and restart so Smart App Control turns on and logging is enabled for troubleshooting.

October Windows update may break Smart App: why it matters now

Smart App Control is the Windows 11 feature that, with Microsoft Defender and SmartScreen, blocks potentially harmful apps or binaries through app intelligence services and code integrity. If KB5127648 has grayed out the Windows Security toggle, a device that had the feature off cannot turn that block back on from the app. Microsoft says devices where Smart App Control is already on are not affected and remain protected. With no fix available yet, the advisory's only steps are temporary workarounds for IT administrators on enterprise-managed devices.

This week Microsoft confirmed that recent Windows updates cause Remote Desktop failures for non-admin users if the "Administrator protection" security feature is enabled. It resolved Always On VPN connection problems after the September 2026 security updates. On Tuesday it addressed black screens, desktop loading issues, and Explorer crashes after Windows 11 updates released since August. Microsoft also reported that Windows KB5124010 crashes some games and apps, and that September updates break audio on some Windows PCs. Both are separate Microsoft faults.

October Windows update may break Smart App: who is affected

The KB5127648 issue applies to some devices running Windows 11, version 24H2 and later, where Smart App Control has been turned off and the Windows Security option is grayed out. Microsoft's advisory says devices where Smart App Control is already turned on are not affected and remain protected. Microsoft said some users may be unable to turn Smart App Control on. The Group Policy packages name Windows 11 versions 24H2, 25H2, and 26H2 as the releases those Feature Preview policies target.

IT administrators on enterprise-managed devices carry the mitigation. They type cmd in the Search box, choose Run as Administrator, and set registry values 2883193997 and 2850574478 to REG_DWORD 1 under HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides, or they enable KB5074105 policies 261015_19222 and 261015_19221. Those policies sit under Computer Configuration > Administrative Templates > {Group Policy name} > Windows 11, version 24H2, 25H2. Both must be Enabled, then each affected device restarted. Devices that already have Smart App Control on do not need either change.

October Windows update may break Smart App: what to watch

A fix has not shipped. Admins who need Smart App Control on after KB5127648 still use registry values 2883193997 and 2850574478, or KB5074105 Feature Preview policies 261015_19222 and 261015_19221, on Windows 11 versions 24H2, 25H2, and 26H2. Both policies must be set to Enabled, and the device must restart before the settings apply. That policy pair is also how logging stays enabled for troubleshooting. Devices that already had Smart App Control turned on should remain protected without either listed workaround.

Recent updates can cause Remote Desktop failures for non-admin users when "Administrator protection" is enabled. Always On VPN problems after the September 2026 security updates are resolved, and Microsoft fixed VPN issues caused by the September Windows updates. Tuesday's fix covers black screens, desktop loading issues, and Explorer crashes after Windows 11 updates released since August. KB5124010 is tied to crashes in some games and apps, and September updates are tied to broken audio on some Windows PCs as well.