Patch tracker / KB5066782

KB5066782: Windows Server 2019 Security Update (December 2025)

KB5066782 is a Critical security update for Windows Server 2019, released 2025-12-09. It closes 103 CVEs with a maximum CVSS of 9.9. At least one of them is actively exploited (CISA KEV), so this is a deploy-first update. The most likely of them to be attacked is CVE-2025-64679, which FIRST.org rates at 6% probability of exploitation in the next 30 days.

Update summary

CriticalCISA KEV

2025-12-09

Released

103

CVEs fixed

9.9

Max CVSS

Critical

Severity

Deploy now

This update fixes vulnerabilities confirmed exploited in the wild.

Fixes 103 CVEs. At least one is actively exploited (CISA KEV). Most severe CVSS 9.9 (Critical). EPSS exploit probability up to 6.0%. Among the top 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: KB5094041 (2026-08-11). 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.

Microsoft is not currently aware of any issues with this update.

The full text, quoted from Microsoft

Microsoft Update Catalog: download KB5066782 Microsoft support article

Senserva AI Opinion for KB5066782

KB5066782 is the December 9, 2025 rollup for Windows 10 Version 1809 and Windows Server 2019, closing 103 CVEs with a top rating of Critical at CVSS 9.9. One of these CVEs, CVE-2025-24990, is listed in the CISA Known Exploited Vulnerabilities catalog, meaning it is being used in real attacks even though EPSS peaks at only 6 percent. Server 2019 domain controllers and legacy 1809 endpoints are directly exposed.

Do this: Deploy KB5066782 to all Windows Server 2019 and Windows 10 1809 systems now, prioritizing the CISA KEV item CVE-2025-24990.

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

Senserva AI Opinion and rich prompt for KB5066782

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 KB5066782 (source: https://senserva.com/kb/5066782.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- Update: KB5066782, Windows Server 2019, released 2025-12-09
- Severity: Critical; fixes 103 CVEs, max CVSS 9.9
- Actively exploited (CISA KEV): YES
- CVEs include: CVE-2016-9535, CVE-2025-24052, CVE-2025-24990, CVE-2025-25004, CVE-2025-47827, CVE-2025-48813, CVE-2025-49708, CVE-2025-50152 and 95 more
- Download: https://catalog.update.microsoft.com/Search.aspx?q=KB5066782
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 KB5066782

Released: 2025-12-09
Last changed: 2026-07-12
Changes tracked: 3

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 KB5066782 is installed

Elevated PowerShell. No output means it is not installed.

# Is KB5066782 installed? (elevated PowerShell)
Get-HotFix -Id KB5066782 -ErrorAction SilentlyContinue

# Across many machines (replace the names):
Invoke-Command -ComputerName SERVER01,SERVER02 {
  Get-HotFix -Id KB5066782 -ErrorAction SilentlyContinue
} | Select-Object PSComputerName, HotFixID, InstalledOn

Known issues, from Microsoft

Quoted from Microsoft's support article for KB5066782 (checked 2026-07-22). Verify against the article before acting.

Microsoft is not currently aware of any issues with this update.

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-2025-24990	High	7.8	6.0%	KEV
CVE-2025-59230	High	7.8	6.0%	KEV
CVE-2025-47827	Medium	4.6	6.0%	KEV
CVE-2016-9535	Critical	9.9	6.0%	No
CVE-2025-49708	Critical	9.9	6.0%	No
CVE-2025-59280	Critical	9.9	6.0%	No
CVE-2025-59294	Critical	9.9	6.0%	No
CVE-2025-58715	High	8.8	6.0%	No
CVE-2025-58716	High	8.8	6.0%	No
CVE-2025-58718	High	8.8	6.0%	No
CVE-2025-59295	High	8.8	6.0%	No
CVE-2025-24052	High	7.8	6.0%	No
CVE-2025-50152	High	7.8	6.0%	No
CVE-2025-50175	High	7.8	6.0%	No
CVE-2025-55328	High	7.8	6.0%	No
CVE-2025-55339	High	7.8	6.0%	No
CVE-2025-55680	High	7.8	6.0%	No
CVE-2025-55692	High	7.8	6.0%	No
CVE-2025-55696	High	7.8	6.0%	No
CVE-2025-55701	High	7.8	6.0%	No
CVE-2025-58714	High	7.8	6.0%	No
CVE-2025-58720	High	7.8	6.0%	No
CVE-2025-58722	High	7.8	6.0%	No
CVE-2025-59187	High	7.8	6.0%	No
CVE-2025-59191	High	7.8	6.0%	No
CVE-2025-59192	High	7.8	6.0%	No
CVE-2025-59199	High	7.8	6.0%	No
CVE-2025-59201	High	7.8	6.0%	No
CVE-2025-59207	High	7.8	6.0%	No
CVE-2025-59242	High	7.8	6.0%	No
CVE-2025-59254	High	7.8	6.0%	No
CVE-2025-59255	High	7.8	6.0%	No
CVE-2025-59275	High	7.8	6.0%	No
CVE-2025-59277	High	7.8	6.0%	No
CVE-2025-59278	High	7.8	6.0%	No
CVE-2025-64679	High	7.8	6.0%	No
CVE-2025-64680	High	7.8	6.0%	No
CVE-2025-59200	High	7.7	6.0%	No
CVE-2025-55326	High	7.5	6.0%	No
CVE-2025-58726	High	7.5	6.0%	No
CVE-2025-55335	High	7.4	6.0%	No
CVE-2025-55687	High	7.4	6.0%	No
CVE-2025-25004	High	7.3	6.0%	No
CVE-2025-59208	High	7.1	6.0%	No
CVE-2025-54957	High	7.0	6.0%	No
CVE-2025-55331	High	7.0	6.0%	No
CVE-2025-55340	High	7.0	6.0%	No
CVE-2025-55678	High	7.0	6.0%	No
CVE-2025-55681	High	7.0	6.0%	No
CVE-2025-55685	High	7.0	6.0%	No
CVE-2025-55686	High	7.0	6.0%	No
CVE-2025-55689	High	7.0	6.0%	No
CVE-2025-58725	High	7.0	6.0%	No
CVE-2025-58730	High	7.0	6.0%	No
CVE-2025-58731	High	7.0	6.0%	No
CVE-2025-58732	High	7.0	6.0%	No
CVE-2025-58733	High	7.0	6.0%	No
CVE-2025-58734	High	7.0	6.0%	No
CVE-2025-58735	High	7.0	6.0%	No
CVE-2025-58736	High	7.0	6.0%	No
CVE-2025-58737	High	7.0	6.0%	No
CVE-2025-58738	High	7.0	6.0%	No
CVE-2025-59193	High	7.0	6.0%	No
CVE-2025-59195	High	7.0	6.0%	No
CVE-2025-59196	High	7.0	6.0%	No
CVE-2025-59202	High	7.0	6.0%	No
CVE-2025-59205	High	7.0	6.0%	No
CVE-2025-59261	High	7.0	6.0%	No
CVE-2025-59282	High	7.0	6.0%	No
CVE-2025-55700	Medium	6.5	6.0%	No
CVE-2025-58717	Medium	6.5	6.0%	No
CVE-2025-58729	Medium	6.5	6.0%	No
CVE-2025-58739	Medium	6.5	6.0%	No
CVE-2025-59185	Medium	6.5	6.0%	No
CVE-2025-59214	Medium	6.5	6.0%	No
CVE-2025-59244	Medium	6.5	6.0%	No
CVE-2025-59259	Medium	6.5	6.0%	No
CVE-2025-48813	Medium	6.3	6.0%	No
CVE-2025-59258	Medium	6.2	6.0%	No
CVE-2025-55332	Medium	6.1	6.0%	No
CVE-2025-55333	Medium	6.1	6.0%	No
CVE-2025-55338	Medium	6.1	6.0%	No
CVE-2025-55325	Medium	5.5	6.0%	No
CVE-2025-55336	Medium	5.5	6.0%	No
CVE-2025-55683	Medium	5.5	6.0%	No
CVE-2025-55695	Medium	5.5	6.0%	No
CVE-2025-55699	Medium	5.5	6.0%	No
CVE-2025-59184	Medium	5.5	6.0%	No
CVE-2025-59186	Medium	5.5	6.0%	No
CVE-2025-59188	Medium	5.5	6.0%	No
CVE-2025-59190	Medium	5.5	6.0%	No
CVE-2025-59197	Medium	5.5	6.0%	No
CVE-2025-59203	Medium	5.5	6.0%	No
CVE-2025-59204	Medium	5.5	6.0%	No
CVE-2025-59209	Medium	5.5	6.0%	No
CVE-2025-59211	Medium	5.5	6.0%	No
CVE-2025-59253	Medium	5.5	6.0%	No
CVE-2025-59260	Medium	5.5	6.0%	No
CVE-2025-62208	Medium	5.5	6.0%	No
CVE-2025-62209	Medium	5.5	6.0%	No
CVE-2025-55679	Medium	5.1	6.0%	No
CVE-2025-59198	Medium	5.0	6.0%	No
CVE-2025-58719	Medium	4.7	6.0%	No

Scope and sources

Affected products

Also released in December 2025

Authoritative references

Official KB5066782 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.

KB5066782: Windows Server 2019 Security Update (December 2025)

Update summary

Full tracking and change history for KB5066782

Check if KB5066782 is installed

Known issues, from Microsoft

CVEs fixed by this update

Scope and sources

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