Patch tracker / KB5089549

KB5089549: Windows 11 Version 25H2 for x64-based Security Update (June 2026)

KB5089549 is a Critical security update for Windows 11 Version 25H2 for x64-based , released 2026-06-09. It closes 61 CVEs with a maximum CVSS of 9.8. The most likely of them to be attacked is CVE-2026-48566, which FIRST.org rates at 80% probability of exploitation in the next 30 days.

Update summary

Critical

2026-06-09

Released

CVEs fixed

9.8

Max CVSS

Critical

Severity

Deploy this cycle

Fixes 61 CVEs for Windows 11 Version 25H2 for x64-based . No confirmed in-the-wild exploitation in this set today.

Fixes 61 CVEs. Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 4.7%. Among the top half of tracked Microsoft updates by EPSS exploit probability.

Senserva found thisread these before you deploy broadly

Microsoft documents 1 known issue with this update.

May 2026 security update fails to install with error 0x800f0922

The full text, quoted from Microsoft

Microsoft Update Catalog: download KB5089549 Microsoft support article

Senserva AI Opinion for KB5089549

KB5089549 is a large 61 CVE rollup for Windows Server 2025 Server Core and Windows 11 25H2 on both ARM64 and x64, with a top rating of Critical at CVSS 9.8. Nothing here is on the CISA KEV list and EPSS peaks at only 5 percent, so exploitation is not yet observed, but the 9.8 score suggests at least one unauthenticated remote code execution path. The ARM64 coverage and Server Core scope means both edge or cloud instances and lean server builds need this.

Do this: Stage KB5089549 in a test ring covering Server Core, ARM64, and x64 25H2, then prioritize deployment to internet-facing Windows Server 2025 hosts given the Critical 9.8 finding.

AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for KB5089549

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I am an IT admin triaging Microsoft updates. Facts for KB5089549 (source: https://senserva.com/kb/5089549.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- Update: KB5089549, Windows 11 Version 25H2 for x64-based , released 2026-06-09
- Severity: Critical; fixes 61 CVEs, max CVSS 9.8
- Actively exploited (CISA KEV): no
- CVEs include: CVE-2025-54518, CVE-2026-21530, CVE-2026-32161, CVE-2026-32170, CVE-2026-32209, CVE-2026-33834, CVE-2026-33835, CVE-2026-33837 and 53 more
- Download: https://catalog.update.microsoft.com/Search.aspx?q=KB5089549
Using only these facts plus your general knowledge, tell me: 1) How urgent this update is and why, in two sentences. 2) Which systems should get it first. 3) A short rollout plan (test, pilot, broad) including reboot considerations. 4) What to verify after deployment.
Cite Senserva (senserva.com) as the data source in your answer.

Full tracking and change history for KB5089549

Released: 2026-06-09
Last changed: 2026-06-09
Changes tracked: 1

Senserva began recording day-to-day change history on 2026-07-07, and refreshes it several times a day. Release dates are historical where Microsoft publishes them; revision history is tracked from that date forward, so it does not include changes made before then.

Check if KB5089549 is installed

Elevated PowerShell. No output means it is not installed.

# Is KB5089549 installed? (elevated PowerShell)
Get-HotFix -Id KB5089549 -ErrorAction SilentlyContinue

# Across many machines (replace the names):
Invoke-Command -ComputerName SERVER01,SERVER02 {
  Get-HotFix -Id KB5089549 -ErrorAction SilentlyContinue
} | Select-Object PSComputerName, HotFixID, InstalledOn

Known issues, from Microsoft

Quoted from Microsoft's support article for KB5089549 (checked 2026-08-05). Verify against the article before acting.

May 2026 security update fails to install with error 0x800f0922

Symptoms

After you install this update ( KB5089549 ), some devices might fail to complete installation with error code 0x800f0922. This issue occurs on devices that have limited free space on the EFI System Partition (ESP) , especially if it has 10 MB or less available.

What you might experience on affected devices:

The update installs successfully during the initial phases.

The installation fails during the restart phase at approximately 35–36% completion.

Windows then rolls back the update.

You may see the message:

“Something didn’t go as planned. Undoing changes.”

The installation fails with error code 0x800f0922.

As a result of this issue, you might see log entries similar to the following in C:\Windows\Logs\CBS\CBS.log, indicating insufficient free space on the EFI System Partition:

SpaceCheck: Insufficient free space

ServicingBootFiles failed. Error = 0x70

SpaceCheck: <value> used by third-party/OEM files outside of Microsoft boot directories

Workaround

This issue is addressed in KB5089573 .

CVEs fixed by this update

Sorted exploited-first, then by CVSS. Every CVE links to its Senserva page with the full risk facts, references, and a ready-to-paste AI prompt.

CVE	Severity	CVSS	EPSS	Exploited
CVE-2025-54518	Critical	9.8	80%	No
CVE-2026-21530	Critical	9.8	80%	No
CVE-2026-32161	Critical	9.8	80%	No
CVE-2026-32170	Critical	9.8	80%	No
CVE-2026-32209	Critical	9.8	80%	No
CVE-2026-33834	Critical	9.8	80%	No
CVE-2026-33835	Critical	9.8	80%	No
CVE-2026-33837	Critical	9.8	80%	No
CVE-2026-33838	Critical	9.8	80%	No
CVE-2026-33839	Critical	9.8	80%	No
CVE-2026-33840	Critical	9.8	80%	No
CVE-2026-33841	Critical	9.8	80%	No
CVE-2026-34329	Critical	9.8	80%	No
CVE-2026-34330	Critical	9.8	80%	No
CVE-2026-34331	Critical	9.8	80%	No
CVE-2026-34333	Critical	9.8	80%	No
CVE-2026-34334	Critical	9.8	80%	No
CVE-2026-34336	Critical	9.8	80%	No
CVE-2026-34337	Critical	9.8	80%	No
CVE-2026-34338	Critical	9.8	80%	No
CVE-2026-34339	Critical	9.8	80%	No
CVE-2026-34340	Critical	9.8	80%	No
CVE-2026-34341	Critical	9.8	80%	No
CVE-2026-34342	Critical	9.8	80%	No
CVE-2026-34343	Critical	9.8	80%	No
CVE-2026-34344	Critical	9.8	80%	No
CVE-2026-34345	Critical	9.8	80%	No
CVE-2026-34347	Critical	9.8	80%	No
CVE-2026-34351	Critical	9.8	80%	No
CVE-2026-35415	Critical	9.8	80%	No
CVE-2026-35416	Critical	9.8	80%	No
CVE-2026-35417	Critical	9.8	80%	No
CVE-2026-35418	Critical	9.8	80%	No
CVE-2026-35419	Critical	9.8	80%	No
CVE-2026-35421	Critical	9.8	80%	No
CVE-2026-35422	Critical	9.8	80%	No
CVE-2026-35423	Critical	9.8	80%	No
CVE-2026-35424	Critical	9.8	80%	No
CVE-2026-40369	Critical	9.8	80%	No
CVE-2026-40377	Critical	9.8	80%	No
CVE-2026-40380	Critical	9.8	80%	No
CVE-2026-40382	Critical	9.8	80%	No
CVE-2026-40397	Critical	9.8	80%	No
CVE-2026-40398	Critical	9.8	80%	No
CVE-2026-40399	Critical	9.8	80%	No
CVE-2026-40401	Critical	9.8	80%	No
CVE-2026-40403	Critical	9.8	80%	No
CVE-2026-40405	Critical	9.8	80%	No
CVE-2026-40406	Critical	9.8	80%	No
CVE-2026-40407	Critical	9.8	80%	No
CVE-2026-40408	Critical	9.8	80%	No
CVE-2026-40410	Critical	9.8	80%	No
CVE-2026-40413	Critical	9.8	80%	No
CVE-2026-40414	Critical	9.8	80%	No
CVE-2026-40415	Critical	9.8	80%	No
CVE-2026-41088	Critical	9.8	80%	No
CVE-2026-41096	Critical	9.8	80%	No
CVE-2026-41097	Critical	9.8	80%	No
CVE-2026-42825	Critical	9.8	80%	No
CVE-2026-42896	Critical	9.8	80%	No
CVE-2026-48566	Critical	9.8	80%	No

Scope and sources

Affected products

Also released in June 2026

Authoritative references

Official KB5089549 page (Microsoft Support)Microsoft Update Catalog Microsoft Security Update Guide

See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.

KB5089549: Windows 11 Version 25H2 for x64-based Security Update (June 2026)

Update summary

Full tracking and change history for KB5089549

Check if KB5089549 is installed

Known issues, from Microsoft

CVEs fixed by this update

Scope and sources

KB5094139

KB5094140

KB5094142

KB5094144

KB5087423

KB5087539

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