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The October 2026 Windows security update is now available

From Microsoft 365 Message Center Archive by Merill Fernando · Microsoft may not have sent this notice to your tenant.
Windows
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What the notice says

Microsoft’s text, safely structured

The October 2026 Windows security update is now available for all supported versions of Windows. We recommend that you install these updates promptly. For more information about the contents of this update, see the release notes, which are accessible from the Windows 11 update history page. To learn more about the different types of monthly quality updates, see Understanding Windows monthly updates.

Highlights for the Windows 11, version 26H2 update

  • This security update includes improvements that were part of update KB5124008 (released September 8, 2026).
  • This update addresses an issue that could cause Always On VPN connections to become stuck in a connecting state or fail to reconnect when automatic protocol selection or fallback was configured.
  • This update fixes an issue in Azure Virtual Desktop and FSLogix environments where Windows Explorer could fail to start after sign-in, resulting in a black screen.
  • This update adds auditing and optional policy controls for ReFS volumes on externally attached storage devices to help organizations prepare for future security hardening changes.
  • This update fixes an issue that could prevent some tiered Storage Spaces Direct virtual disks from coming online after installing certain security updates, affecting clustered workloads.

Short on time? Watch the Windows 11 release notes video for this month’s tips.

For instructions on how to install this update, see the KB article for your operating system listed below:

  • Windows 11, versions 26H2, 25H2, and 24H2: KB5127648
  • Windows 11, version 26H1: KB5127646
  • Windows 11, version 23H2: KB5126653
  • Windows 10, versions 22H2 and 21H2: KB5126657
  • Windows 11 Enterprise LTSC 2024: Baseline KB5131362
  • Windows 10 Enterprise LTSC 2019 and Windows Server 2019: KB5126651
  • Windows 10 LTSB 2016 and Windows Server 2016: KB5126868
  • Windows Server 2025: KB5126646
  • Windows Server 2025 Datacenter: Azure Edition: Baseline KB5131334
  • Windows Server 2022: KB5126655
  • Windows Server 2022 Datacenter: Azure Edition: Baseline KB5126655
  • Windows Server 2012 R2: KB5126836
  • Windows Server 2012: KB5126835

Note: With recent and upcoming Windows updates over the next few months, a limited number of consumer and business devices might experience one additional restart during installation. This one‑time restart occurs after a Secure Boot certificate update is applied as part of the Secure Boot update process.

What changed

Between archive captures, newest first

The archive supplies one version of this notice.

Learn more

Links from the notice and their documentation checks

Shared KB KB5124008

Shared KB KB5126646 (5 items)

Not confirmed here

What this page cannot tell you
  • Whether your tenant is affected: this is Microsoft's notice, not a check of your settings.
  • 16 linked pages have not been read yet.
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