Description: Can't switch Smart App Control back on after the October 2026 Windows 11 update? Check KB5127648, affected builds, Microsoft's registry or Group Policy workaround, and why a PC reset should not be your first step.
Microsoft has confirmed that the October 13, 2026 Windows 11 security update KB5127648 can leave the Smart App Control “On” option greyed out on some PCs where the feature was previously off. PCs that already had it enabled remain protected. As checked on October 18, Microsoft has published temporary workarounds but has not announced a permanent fix.[1]
Affected versions: check the build, not just the laptop brand
| Windows 11 | Build with KB5127648 | Documented symptom |
|---|---|---|
| 24H2 | 26100.9711 |
Previously disabled Smart App Control cannot be switched on on some PCs |
| 25H2 | 26200.9711 |
Same condition |
| 26H2 | 26300.9711 |
Same condition |
Microsoft has not identified specific manufacturers, processors, or affected percentages. This is a problem with re-enabling a disabled feature, not a statement that the update disables protection on every PC.[1]
Check your PC without changing anything
- Press
Win + R, enterwinver, and note the Windows version and OS build. - Go to Settings → Windows Update → Update history. Look for
KB5127648and compare it with the build. - Open Windows Security → App & browser control → Smart App Control settings. Check whether the feature is On, Evaluation, or Off and whether On is selectable.[1][2]
| What you see | What it means |
|---|---|
| Smart App Control is On | This known issue does not affect your enabled protection. Leave it on. |
| Off, and On is greyed out after KB5127648 | Matches the officially documented regression; review Microsoft's mitigation. |
| Off on a work PC, or long before this update | Check management policies, developer mode, eligibility, and diagnostic settings before blaming the update. |
Confirmed facts versus user reports
Microsoft confirms the symptom and update relationship, but has not published an internal root cause or a device-by-device reproduction matrix. In a public WindowsUpdate discussion, one person said that after the October update Windows began asking for a reinstall before re-enabling the feature. That is an individual report, not proof that every affected PC behaves identically.[1][4]
A confusing detail: Microsoft's general App & browser control page still includes older wording about needing to reinstall Windows. Its more recent Smart App Control FAQ explicitly says recent Windows updates allow re-enabling without a clean installation. Returning to Evaluation mode and enabling an eligible Off feature are also different operations. Read the current KB advisory for this specific October problem.[2][3]
Safe next steps and Microsoft's workarounds
For a personal PC, check Windows Update and the current KB page first. Microsoft's temporary fix adds two REG_DWORD overrides, 2883193997 and 2850574478, both set to 1 under HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides, then restarts Windows. Registry editing requires administrator rights and can cause problems if performed incorrectly. Follow the current commands on Microsoft's page [1] only after reading its backup and recovery guidance [5]; avoid copying commands from an unverified forum.
For a managed device, the IT team can use Microsoft's two special Group Policy packages, KB5074105 261015_19222 and 261015_19221. Microsoft says both are required: one restores the ability to turn the feature on, and the other supports troubleshooting logs. Do not override workplace security policy yourself.[1]
Avoid resetting Windows just to recover the switch, and do not uninstall a security update as your first response. A reset or reinstall can remove apps and settings and may affect files depending on the options chosen; uninstalling the update removes security fixes. Windows 11 24H2 Home and Pro also received their final monthly security update in October 2026, so plan a move to a supported release.[1]
Bottom line
If Smart App Control is stuck Off after KB5127648, confirm the build and the previous setting before changing anything. Microsoft recognizes the issue and provides temporary mitigations. Already-enabled protection stays enabled; everyone else should prefer the official guidance and an administrator-assisted fix over a reset.
References (1)
[1] Microsoft, KB5127648 release notes and known issues: https://support.microsoft.com/en-us/servicing/os/windows-11/2026/10/kb5127648-windows-11-24h2-25h2-26h2-security-update [2] Microsoft, App & browser control: https://support.microsoft.com/en-us/windows/security/windows-security/app-browser-control-in-the-windows-security-app [3] Microsoft, Smart App Control FAQ: https://support.microsoft.com/en-us/windows/security/threat-malware-protection/smart-app-control-frequently-asked-questions [4] Individual user observation, October 15: https://www.reddit.com/r/WindowsUpdate/comments/1x70ige/did_the_october_update_change_smart_app_control/ [5] Microsoft, Registry backup and recovery: https://support.microsoft.com/en-us/windows/experience/backup-recovery/how-to-back-up-and-restore-the-registry-in-windows
