Patch tracker / KB5087420

KB5087420: Windows Server 2019 Security Update (May 2026)

KB5087420 is a Critical security update for Windows Server 2019, released 2026-05-12. It closes 56 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 56 CVEs for Windows Server 2019. No confirmed in-the-wild exploitation in this set today.

Fixes 56 CVEs. Most severe CVSS 9.8 (Critical). EPSS exploit probability up to 2.4%. Among the lower half 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.

Devices with an unrecommended BitLocker Group Policy configuration might be required to enter their BitLocker recovery key

The full text, quoted from Microsoft

Microsoft Update Catalog: download KB5087420 Microsoft support article

Senserva AI Opinion for KB5087420

KB5087420 is a large rollup for Windows 10 Version 1809 and Windows Server 2019 that closes 56 CVEs, with the worst rated Critical at CVSS 9.8, meaning unauthenticated remote code execution is plausible. Nothing here is in the CISA KEV catalog or tied to ransomware, and the highest EPSS is only 2 percent, so there is no confirmed exploitation yet. The exposure matters because 1809 and Server 2019 are common in longer-lived infrastructure where patching lags.

Do this: Deploy KB5087420 to your Windows 10 1809 and Server 2019 hosts this cycle, prioritizing any internet-facing Server 2019 systems that could be hit by the CVSS 9.8 remote code execution flaw.

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

Senserva AI Opinion and rich prompt for KB5087420

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 KB5087420 (source: https://senserva.com/kb/5087420.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- Update: KB5087420, Windows Server 2019, released 2026-05-12
- Severity: Critical; fixes 56 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 48 more
- Download: https://catalog.update.microsoft.com/Search.aspx?q=KB5087420
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 KB5087420

Released: 2026-05-12
Last changed: 2026-05-12
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 KB5087420 is installed

Elevated PowerShell. No output means it is not installed.

# Is KB5087420 installed? (elevated PowerShell)
Get-HotFix -Id KB5087420 -ErrorAction SilentlyContinue

# Across many machines (replace the names):
Invoke-Command -ComputerName SERVER01,SERVER02 {
  Get-HotFix -Id KB5087420 -ErrorAction SilentlyContinue
} | Select-Object PSComputerName, HotFixID, InstalledOn

Known issues, from Microsoft

Quoted from Microsoft's support article for KB5087420 (checked 2026-08-05). Verify against the article before acting.

Devices with an unrecommended BitLocker Group Policy configuration might be required to enter their BitLocker recovery key

Symptom

Some devices with an unrecommended BitLocker Group Policy configuration might be required to enter their BitLocker recovery key on the first restart after installing this update.

This issue only affects a limited number of systems in which ALL of the following conditions are true. These conditions are unlikely to be found on personal devices not managed by IT departments.

BitLocker is enabled on the OS drive.

The Group Policy " Configure TPM platform validation profile for native UEFI firmware configurations " is configured, and PCR7 is included in the validation profile (or the equivalent registry key is set manually).

System Information ( msinfo32.exe ) reports Secure Boot State PCR7 Binding as " Not Possible ".

The Windows UEFI CA 2023 certificate is present in the device’s Secure Boot Signature Database (DB), making the device eligible for the 2023‑signed Windows Boot Manager to be made the default.

The device is not already running the 2023-signed Windows Boot Manager.

In this scenario, the BitLocker recovery key only needs to be entered once -- subsequent restarts will not trigger a BitLocker recovery screen, as long as the group policy configuration remains unchanged. For help finding your BitLocker recovery key, see the article, Find your ...

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-2026-33841	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-2026-35421	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-2026-40402	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-2026-41088	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

Scope and sources

Affected products

Also released in May 2026

Authoritative references

Official KB5087420 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.

KB5087420: Windows Server 2019 Security Update (May 2026)

Update summary

Full tracking and change history for KB5087420

Check if KB5087420 is installed

Known issues, from Microsoft

CVEs fixed by this update

Scope and sources

KB5002863

KB5002868

KB5002870

KB5078943

KB5087424

KB5087470

KB5087471

KB5087537