If Smart App Control is greyed out in Windows Security after the October update, you’re not imagining it. Microsoft has confirmed that KB5127648 can leave the toggle locked on some PCs, and it has published a workaround.
The bug only hits PCs where Smart App Control was already off. If it was on before you updated, you’re fine.
Here are the facts you need at a glance:
- Update: KB5127648, the October 2026 Patch Tuesday release (October 13).
- Affected: Windows 11 24H2, 25H2 and 26H2 with Smart App Control switched off.
- Symptom: the Smart App Control option can’t be turned on.
- Fix: a registry workaround exists; a permanent patch has no date yet.
What exactly is broken?
Smart App Control is the Windows 11 feature that blocks untrusted and potentially harmful apps. After installing KB5127648, some devices can’t switch it back on. The option in Windows Security appears greyed out.
Microsoft added the problem to the KB5127648 support page as a known issue. According to gHacks, Microsoft hasn’t shared a root cause or a date for a permanent fix.
Don’t confuse this with the security fix itself. We covered why that patch matters in our KB5127648 zero-day guide, and this bug doesn’t change the advice to install it.
Are you affected?
Check which of these describes your PC. Only the last row is a problem.
| Your situation | Affected? |
|---|---|
| Smart App Control was on before the update | No, it keeps working |
| Smart App Control was off, and you do not want it | No action needed |
| Smart App Control was off, and you want it on now | Yes, the toggle may be greyed out |
Most people who turned the feature off did so because it blocked an app they trusted. If that’s you, you may not care about this bug at all.
How to fix Smart App Control greyed out on Windows 11
The home-user fix is a pair of registry values. As reported by BetaNews, Microsoft’s steps are below. Back up your registry first, because a wrong edit can cause problems.
Open the Start menu, type cmd, and choose Run as administrator. Then run these two commands, one after the other:
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 /fRestart the PC, then open Windows Security, go to App & browser control, and turn Smart App Control on. The toggle should now respond.
These values live in the same key Windows uses for Known Issue Rollback. Here they force two features on rather than roll something back, so treat them as a temporary patch.
What IT admins should do
Managed PCs use Group Policy instead. Microsoft’s route is to install two Feature Preview packages listed under KB5074105, then set both policies to Enabled and restart.
One package re-enables Smart App Control. The other turns on logging so you can troubleshoot. The packages cover Windows 11 24H2, 25H2 and 26H2.
The exact policy path wasn’t clear in the coverage we read, so check Microsoft’s KB5127648 page before rolling this out.
Should you turn Smart App Control on at all?
It’s a fair question. Smart App Control adds a strong layer against unknown apps, but it can block software you actually use, especially tools from small developers.
If you’re considering a clean start to get the feature working, our Windows 11 cloud rebuild guide explains that route. For most people, though, the registry fix is far less work.
Frequently Asked Questions
Why is Smart App Control greyed out after the October update?
Microsoft says KB5127648 can stop some devices from turning it on if it was off before the update. No cause has been published.
Is there a permanent fix?
Not yet. Microsoft has only said a fix is coming, with no date.
Is the registry workaround safe?
It’s Microsoft’s own published workaround, but any registry edit carries some risk. Back up first and run the commands exactly as shown.
Should I uninstall KB5127648 to fix it?
No. The update includes security fixes, and removing it leaves you exposed. Use the workaround instead.
If you want Smart App Control on, apply the registry fix and move on. If you left it off on purpose, skip all of this and wait for Microsoft’s patch. Either way, keep KB5127648 installed.
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