MC1308634 – M365 Change Digest

One-line summary

The May 2026 Windows security update is available, with security fixes, boot reliability, and Secure Boot certificate rollout improvements; install promptly to ensure device protection.

Similar updates

Details

Body (from Message Center)

The May 2026 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 easily accessible from the Windows 11 update history page. To learn more about the different types of monthly quality updates, see Windows monthly updates explained.

Highlights for the Windows 11, version 25H2 update:

This security update includes improvements that were a part of update KB5083631 (released April 30, 2026).
This update makes quality improvements to the servicing stack, which is the component that installs Windows updates.
This update expands high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Devices receive the new certificates only after demonstrating sufficient successful update signals, maintaining a controlled and phased rollout.
This update improves startup reliability after boot file updates, so devices start normally without entering BitLocker recovery.
This update improves the reliability of Simple Service Discovery Protocol (SSDP) notifications to help prevent the service from becoming unresponsive.

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

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

Windows 11, version 26H1: KB5089548
Windows 11, versions 25H2 and 24H2: KB5089549
Windows 11, version 23H2: KB5087420
Windows 11 Enterprise LTSC 2024: Hotpatch KB5089466
Windows 10, versions 22H2 and 21H2: KB5087544
Windows 10 Enterprise LTSC 2019 and Windows Server 2019: KB5087538
Windows 10 LTSB 2016 and Windows Server 2016: KB5087537
Windows Server 2025: KB5087539
Windows Server 2025 Datacenter: Azure Edition: Hotpatch KB5087423
Windows Server 2022: KB5087545
Windows Server 2022 Datacenter: Azure Edition: Hotpatch KB5087424
Windows Server 2012 R2: KB5087471
Windows Server 2012: KB5087470

Note: With recent and upcoming Windows updates, 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.

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{
  "snapshot_item": {
    "action_required_by": null,
    "ai_action_required_by": "2026-05-31T00:00:00Z",
    "ai_actions": [
      "Review release notes",
      "Install May 2026 security update on all supported devices",
      "Inform users about possible extra restart with Secure Boot update"
    ],
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    "ai_model": "gpt-4.1",
    "ai_summary": "The May 2026 Windows security update is available, with security fixes, boot reliability, and Secure Boot certificate rollout improvements; install promptly to ensure device protection.",
    "ai_topics": [
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    ],
    "category": "stayInformed",
    "details_map": {},
    "id": "MC1308634",
    "importance": 5,
    "is_major_change": true,
    "last_modified": "2026-05-12T17:12:03Z",
    "ms_products": [
      "Windows"
    ],
    "platforms": null,
    "roadmap_ids": [],
    "services": [
      "Windows"
    ],
    "severity": "normal",
    "tags": [
      "Admin impact"
    ],
    "title": "The May 2026 Windows security update is now available"
  }
}