Patch tracker / KB5087537

KB5087537: Windows Server 2019 Security Update (May 2026)

KB5087537 is a Critical security update for Windows Server 2019, released 2026-05-12. It closes 47 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 47 CVEs for Windows Server 2019. No confirmed in-the-wild exploitation in this set today.

Fixes 47 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.

Domain Controller lookup might fail for 15-character hostnames

The full text, quoted from Microsoft

Microsoft Update Catalog: download KB5087537 Microsoft support article

Senserva AI Opinion for KB5087537

KB5087537 is the May 2026 rollup for Windows 10 1809 and Windows Server 2019, fixing 47 CVEs including one rated Critical at CVSS 9.8 with an 80 percent EPSS score, meaning exploitation is statistically likely even though nothing here is yet in CISA KEV. The 1809 branch and Server 2019 tend to linger in stable server fleets, so domain controllers and legacy application hosts are the exposed population. The high EPSS on the top CVE is the reason to move quickly rather than waiting for a KEV listing.

Do this: Prioritize this rollup on any remaining Server 2019 domain controllers and 1809 hosts, testing in a pilot ring today and scheduling broad deployment within the week.

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

Senserva AI Opinion and rich prompt for KB5087537

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 KB5087537 (source: https://senserva.com/kb/5087537.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- Update: KB5087537, Windows Server 2019, released 2026-05-12
- Severity: Critical; fixes 47 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-2026-33837, CVE-2026-33838 and 39 more
- Download: https://catalog.update.microsoft.com/Search.aspx?q=KB5087537
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 KB5087537

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 KB5087537 is installed

Elevated PowerShell. No output means it is not installed.

# Is KB5087537 installed? (elevated PowerShell)
Get-HotFix -Id KB5087537 -ErrorAction SilentlyContinue

# Across many machines (replace the names):
Invoke-Command -ComputerName SERVER01,SERVER02 {
  Get-HotFix -Id KB5087537 -ErrorAction SilentlyContinue
} | Select-Object PSComputerName, HotFixID, InstalledOn

Known issues, from Microsoft

Quoted from Microsoft's support article for KB5087537 (checked 2026-08-06). Verify against the article before acting.

Domain Controller lookup might fail for 15-character hostnames

Symptoms

After installing this update, domain controller discovery might fail on Windows Server 2016 systems when the server hostname is 15 characters long.

When the hostname is 15 characters long, DCLocator calls (for example, using nltest /dsgetdc:<domain> /pdc ) will return ERROR_INVALID_PARAMETER, preventing applications and administrative tools from locating a domain controller. As a result, administrative operations that rely on domain controller lookup might fail, impacting scenarios such as DFS Namespace management.

Resolution

This issue is resolved in Windows updates released on and after June 9, 2026 ( KB5094122 ). We recommend you install the latest Windows update for your device as it contains important improvements and issue resolutions, including this one.

Applies to: Windows 10 Enterprise LTSB 2016 and Windows 10 IoT Enterprise 2016 LTSB

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

April 14, 2026—KB5082198 (OS Build 14393.9060)

The following is a summary of the issues that this update addresses. 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 ...

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-2026-33837	Critical	9.8	80%	No
CVE-2026-33838	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-2026-34338	Critical	9.8	80%	No
CVE-2026-34339	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-2026-35420	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-2026-41089	Critical	9.8	80%	No
CVE-2026-41095	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 KB5087537 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.

KB5087537: Windows Server 2019 Security Update (May 2026)

Update summary

Full tracking and change history for KB5087537

Check if KB5087537 is installed

Known issues, from Microsoft

CVEs fixed by this update

Scope and sources

KB5002863

KB5002868

KB5002870

KB5078943

KB5087420

KB5087424

KB5087470

KB5087471