Microsoft: October Windows Update May Break Smart App Control

Microsoft says some Windows 11 devices may be unable to turn on Smart App Control after installing the October security update KB5127648.

The issue affects devices running Windows 11, version 24H2 and later, where Smart App Control was previously turned off. On affected devices, its option in the Windows Security app may appear grayed out and cannot be toggled. Microsoft says devices where the feature is already turned on are not affected and remain protected.

Smart App Control uses Microsoft's app intelligence services and code integrity features. It works alongside Microsoft Defender and SmartScreen to block potentially harmful apps or binaries.

Microsoft has not yet provided a fix. For enterprise-managed devices, IT administrators can use temporary workarounds involving registry changes or Group Policy settings to restore the option. Microsoft says administrators must enable both Group Policy settings and restart affected devices for the policies to apply.

The company also recently reported other Windows update issues, including Remote Desktop failures for non-admin users when Administrator protection is enabled, and VPN connection problems after September 2026 security updates. Microsoft says it resolved the VPN issue.