Fix Smart App Control Grayed Out After KB5127648

October’s update locked the Smart App Control toggle. One update fixes 25H2 and 26H2. Two registry values fix 24H2.

Tech fix: if the Smart App Control toggle is grayed out after the October 13, 2026 security update KB5127648, install KB5127936 on Windows 11 25H2 or 26H2. On 24H2, add two registry values and restart. Both fixes are below.

Microsoft confirmed the bug as a known issue. It only hits devices where Smart App Control was already off. Devices where Smart App Control is already on are not affected and stay protected.

Windows 11 version	Affected build from KB5127648	Fix
24H2	26100.9711	Registry workaround or Group Policy below
25H2	26200.9711	Install KB5127936, build 26200.9818 or later
26H2	26300.9711	Install KB5127936, build 26300.9818 or later

Quick Fix for 25H2 and 26H2

Open Settings, then Windows Update, and check for updates. KB5127936 is the October 28, 2026 preview update, so it shows up as an optional download. Install it and restart. Microsoft says that once this update or a later one is installed, no workaround is needed.

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Run that from the Start menu to confirm the build. You want 26200.9818 or higher on 25H2, or 26300.9818 or higher on 26H2.

Quick Fix for 24H2: The Registry Workaround

Microsoft says to back up the registry before changing it. Its guide is How to back up and restore the registry in Windows. Then type cmd in the Search box, select Run as administrator, and enter these two commands exactly as Microsoft publishes them:

reg add "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2883193997 /t REG_DWORD /d 1 /f
reg add "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2850574478 /t REG_DWORD /d 1 /f

Restart the device. The same workaround applies to 25H2 and 26H2 machines that are still on an update older than KB5127936.

One more thing for 24H2: Microsoft’s release health page says Home and Pro editions of 24H2 reached end of updates on October 13, 2026. Those PCs will not get a fix through Windows Update. Moving them to 25H2 or 26H2 solves this bug and keeps security updates coming.

Group Policy for Managed Devices

For enterprise-managed devices, Microsoft offers two special Group Policy packages as an alternative to the registry edit. Both are listed in the KB5127648 article for Windows 11 24H2, 25H2, and 26H2:

Download #1: KB5074105 261015_19222 Feature Preview

Download #2: KB5074105 261015_19221 Feature Preview

Microsoft says to install and configure both. The first one turns on Smart App Control. The second keeps logging available for troubleshooting. After installing, find them under Computer Configuration > Administrative Templates > the Group Policy name > Windows 11, version 24H2, 25H2. Set both to Enabled and restart the devices.

Check That It Worked

Open Windows Security, then App & browser control, then Smart App control settings. The toggle should be selectable again. If you want it on, turn it on there.

Rolling Back the Registry Change

Once a device has a fixed build, or if you want to undo the workaround, delete the two override values from an administrator Command Prompt and restart:

reg delete "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2883193997 /f
reg delete "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2850574478 /f

You can also restore the backup you made before the change.

What Happened

The October 13, 2026 security update KB5127648 shipped as OS Builds 26100.9711, 26200.9711, and 26300.9711. Microsoft lists the Smart App Control problem as a known issue in that article: on some devices where Smart App Control was turned off, the option to turn it back on in Windows Security is grayed out.

The fix arrived in KB5127936, the October 28 preview for 25H2 and 26H2, OS Builds 26200.9818 and 26300.9818. Its notes say it fixes the issue where you might be unable to turn on Smart App Control after it has been turned off. The KB5127648 article still names 24H2 as needing the workaround. For the rest of this month’s bugs, see our roundup of October 2026 Patch Tuesday known issues.

If That Didn’t Work

A grayed-out toggle has other causes that predate this update. Microsoft’s Smart App Control FAQ lists these reasons it can be off:

Managed device or developer mode. Your device is enterprise-managed, or developer mode has been configured. On a work PC, your IT team controls this setting.

Turned off by a user. You or someone else signed in to the PC switched it off.

S mode. Microsoft says to turn S mode off, then reset the PC.

Optional diagnostic data is off. Microsoft says to reset or reinstall Windows and choose Send optional diagnostic data during setup.

Microsoft also says Windows can turn Smart App Control off on its own for corporate users and developers whose regular work would trigger too many blocks.

The old rule that a clean install was the only way back has changed. The FAQ now says recent Windows updates allow Smart App Control to be turned back on in the Windows Security app without a clean installation. If your PC is fully updated, not managed, and the toggle is still gray, start with the registry workaround above.