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Windows 11 Smart App Control grayed out after KB5127648: fixed for 25H2/26H2 by KB5127936

LLa rédaction TricknFix OPPublished 4 min de lecture
Editorial illustration of a Windows security shield and a grayed toggle, suggesting Smart App Control stuck off after a Windows update.
Crédit : TricknFix — illustration éditoriale

After the October 2026 security update KB5127648, some PCs could not turn Smart App Control back on (option grayed out). Microsoft fixed it for Windows 11 25H2 and 26H2 with KB5127936 (preview dated Oct 28; updates on/after Oct 27). 24H2 still uses the documented workaround path.

Microsoft documents a Smart App Control known issue after the October 2026 Windows 11 security update KB5127648: on some devices where Smart App Control was off, you might be unable to turn it back on in the Windows Security app — the option can appear grayed out. Devices where Smart App Control was already on are not affected and remain protected.
The issue is resolved for Windows 11 versions 26H2 and 25H2 by Windows updates released on and after 27 October 2026, specifically KB5127936. If you install KB5127936 or a later update, Microsoft says you do not need the workaround for this issue.
This article focuses on that known issue and fix. It does not rehash other items already covered on TricknFix from the same preview package (File Explorer customizable context menu, Cloud rebuild, restore summary).

What broke after KB5127648

According to the KB5127648 known-issues page:
  • After installing the update, some devices might be unable to turn Smart App Control back on if it has been turned off.
  • On affected devices, the option to turn it on might be grayed out.
  • Devices where Smart App Control is already turned on are not affected and remain protected.
No hands-on reproduction is claimed here. Facts follow Microsoft’s support notes as consulted on 6 November 2026 (Europe/Paris).
Smart App Control eligibility and prerequisites are defined by Microsoft (see the product FAQ). This article does not invent who can enable SAC on a given PC.

The fix for Windows 11 25H2 and 26H2: KB5127936

Microsoft’s resolution text on KB5127648 states the issue was resolved for Windows 11, versions 26H2 and 25H2, by updates released on and after 27 October 2026 (KB5127936). Installing that update or a later one removes the need for the workaround.
The KB5127936 preview page (dated 28 October 2026) lists:
  • Applies to Windows 11 version 26H2 and 25H2 (all editions listed on that page).
  • OS builds 26300.9818 (26H2) and 26200.9818 (25H2).
  • Under normal rollout: [Smart App Control (Known issue)] Fixed — same grayed-out symptom when trying to turn SAC back on after it was off.
How Microsoft documents obtaining the optional preview: open Start > Settings > Windows Update > Advanced options > Optional updates, then check for available optional updates.
Important scope note from the same KB: starting with the October 2026 release, non-security preview updates are available only for Windows 11 versions 25H2 and 26H2. Windows 11 version 24H2 no longer receives those non-security preview updates (Enterprise and Education continue monthly security updates).

If you are on 24H2, or still on a pre–27 October update

If you are using Windows 11 version 24H2, or an update released before 27 October 2026, and you still have this issue, Microsoft documents workarounds on the KB5127648 page. Prefer installing a fixed update when your channel offers one; use workarounds only when Microsoft’s path applies.

Registry workaround (administrator only — not a casual tip)

Microsoft labels this section Important and warns that it modifies the registry. Back up the registry and know how to restore it before changing anything (Microsoft links its “How to back up and restore the registry in Windows” guidance).
Documented steps (paraphrased to match Microsoft’s commands):
  1. Open Command Prompt as administrator.
  2. Run: reg add "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2883193997 /t REG_DWORD /d 1 /f
  3. Run: reg add "HKLM\SYSTEM\CurrentControlSet\Policies\Microsoft\FeatureManagement\Overrides" /v 2850574478 /t REG_DWORD /d 1 /f
  4. Restart the device.
Do not treat registry edits as a general Windows tip. Use them only for this documented issue when you are on the 24H2 / pre–27 October path Microsoft describes, and only with admin rights and a backup.

Group Policy path for IT-managed devices

For enterprise-managed devices, Microsoft documents installing and configuring both special Group Policies listed on KB5127648 (Feature Preview downloads associated with KB5074105). Microsoft states both are required: one to turn Smart App Control back on, and one so logging remains available for troubleshooting. Follow the exact download and policy configuration steps on the support page — this article does not invent GPO paths beyond that reference.

Other KB5127936 items already on TricknFix

KB5127936 is a large preview. Separate TricknFix articles already cover other features from that package; they are different intents:

Sources

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