Patch tracker / KB5087538

KB5087538: Windows Server 2019 Security Update (May 2026)

KB5087538 is a Critical security update for Windows Server 2019, released 2026-05-12. It closes 55 CVEs with a maximum CVSS of 9.8. The most likely of them to be attacked is CVE-2026-33834, which FIRST.org rates at 80% probability of exploitation in the next 30 days.

Update summary

Critical

2026-05-12

Released

CVEs fixed

9.8

Max CVSS

Critical

Severity

Deploy this cycle

Fixes 55 CVEs for Windows Server 2019. No confirmed in-the-wild exploitation in this set today.

Fixes 55 CVEs. Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 80%. Among the top 10% of tracked Microsoft updates by EPSS exploit probability.

Senserva found thiswe track every release for this product line, so we can tell you this package is behind

A newer security update for Windows 10 Version 1809 for 32-bit Systems has shipped since this one: KB5089548 (2026-07-14). For cumulative update families the newer package includes these fixes, so installing that one is usually the shorter path. Verify against your own update rings before you skip this package.

Senserva found thisread these before you deploy broadly

Microsoft documents 1 known issue with this update.

We are currently not aware of any issues with this update.

The full text, quoted from Microsoft

Microsoft Update Catalog: download KB5087538 Microsoft support article

Senserva AI Opinion for KB5087538

KB5087538 is a large rollup for Windows 10 Version 1809 and Windows Server 2019 that closes 55 CVEs, with the worst rated Critical at CVSS 9.8 and an 80 percent EPSS score indicating that exploitation is likely soon. No CVE here is on the CISA KEV list or tied to ransomware yet, but that high EPSS combined with the 9.8 remote severity puts Server 2019 domain controllers and file servers in the direct line of fire.

Do this: Test and deploy KB5087538 to your 1809 and Server 2019 hosts this cycle, prioritizing internet-facing and server roles given the 9.8 CVSS and 80 percent EPSS.

AI-generated from public data, 2026-07-26. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for KB5087538

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 KB5087538 (source: https://senserva.com/kb/5087538.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- Update: KB5087538, Windows Server 2019, released 2026-05-12
- Severity: Critical; fixes 55 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 47 more
- Download: https://catalog.update.microsoft.com/Search.aspx?q=KB5087538
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 KB5087538

Released: 2026-05-12
Last changed: 2026-07-24
Changes tracked: 2

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 KB5087538 is installed

Elevated PowerShell. No output means it is not installed.

# Is KB5087538 installed? (elevated PowerShell)
Get-HotFix -Id KB5087538 -ErrorAction SilentlyContinue

# Across many machines (replace the names):
Invoke-Command -ComputerName SERVER01,SERVER02 {
  Get-HotFix -Id KB5087538 -ErrorAction SilentlyContinue
} | Select-Object PSComputerName, HotFixID, InstalledOn

Known issues, from Microsoft

Quoted from Microsoft's support article for KB5087538 (checked 2026-08-05). Verify against the article before acting.

We are currently not aware of any issues with this update.

Applies to: Windows 10 Enterprise LTSC 2019

This security update includes fixes and quality improvements that are part of the following update:

April 14, 2026—KB5082123 (OS Build 17763.8644)

The following is a summary of the issues that this update addresses when you install this update. The bold text within the brackets indicates the item or area of the change we are documenting.

[Remote Desktop security warnings (known issue)] Fixed: The Remote Desktop Connection security warning dialog might render incorrectly in multi-monitor configurations with different display scaling settings. This issue might occur after installing the Windows security update released on or after April 14, 2026 (such as KB5082123 ).

[Secure Boot]

This update enables dynamic status reporting for Secure Boot states in Windows Security App.

With this update, Windows quality updates include additional 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 adds a new SecureBoot folder under C:\Windows on eligible devices. The folder contains example scripts intended for organizations with IT professionals who ...

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-2026-34329	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-2026-35420	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-2026-40377	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-2026-40406	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-2026-41089	Critical	9.8	80%	No
CVE-2026-41095	Critical	9.8	80%	No
CVE-2026-41097	Critical	9.8	80%	No
CVE-2026-42825	Critical	9.8	80%	No

Scope and sources

Affected products

Also released in May 2026

Authoritative references

Official KB5087538 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.

KB5087538: Windows Server 2019 Security Update (May 2026)

Update summary

Full tracking and change history for KB5087538

Check if KB5087538 is installed

Known issues, from Microsoft

CVEs fixed by this update

Scope and sources

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