Patch tracker / KB5055561
KB5055561: Windows Server 2019 Security Update (April 2025)
KB5055561 is a High security update for Windows Server 2019, released 2025-04-08. It closes 42 CVEs with a maximum CVSS of 8.8. At least one of them is actively exploited (CISA KEV) and linked to ransomware, so this is a deploy-first update. Get it from the Microsoft Update Catalog below, and see where it sits against the rest of the month on the patch tracker.
Microsoft security update released 2025-04-08. Fixes 42 CVEs.
Exploitation is not theoretical here: at least one CVE this update fixes is on the CISA Known Exploited Vulnerabilities catalog, which means attackers are already using it against unpatched systems, including in ransomware campaigns. For an update like this, the risk window is the gap between today and the day your last device installs it, so shortening that gap matters more than perfect scheduling.
Most organizations deliver an update like this automatically through Intune update rings, Windows Update for Business, Windows Autopatch, or WSUS; the install section below covers each path, including how to expedite it for the exploited CVE. For the bigger picture: how the Microsoft patching tools fit together, this month's Patch Tuesday summary, and every update ranked by real-world risk.
Updated July 24, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Download KB5055561
Get the official update for KB5055561. The download and file size for each supported product are on the Microsoft Update Catalog page.
Update summary
Senserva AI Opinion for KB5055561
KB5055561 closes 42 CVEs for April 2025 on Windows 10 1809 and Windows Server 2019, High severity at CVSS 8.8, 18 percent EPSS, with the CISA KEV listing and ransomware linkage shared across this entire monthly family. This sits in the middle of the CVE-count range for this batch of April builds, reinforcing that Microsoft split one large fix set across many overlapping packages. The ransomware tie is the fact that should drive scheduling here, not the specific CVE count.
Do this: Schedule KB5055561 with the same urgency as the largest April 2025 builds, since the ransomware linkage applies regardless of CVE count.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5055561
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5055561
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.
Exploitation and severity
Fixes 42 CVEs. At least one is actively exploited (CISA KEV). Most severe CVSS 8.8 (High). EPSS exploit probability up to 13%. One is linked to ransomware.
Among the top half of tracked Microsoft updates by EPSS exploit probability.
What to do
Treat as urgent: it is being exploited in the wild (CISA KEV), so patch ahead of items that are not. Senserva flags whether KB5055561 is missing on your devices.
Check if KB5055561 is installed
Copy-paste PowerShell: one machine, or your whole fleet in one pass. No output means the update is not installed.
Get-HotFix covers Windows updates. Office, SharePoint, and Exchange server updates show under installed updates in Programs and Features, or check the Update Catalog history.
Known issues, from Microsoft
Quoted from Microsoft's support article for KB5055561 (checked 2026-07-22). Verify against the article before acting.
We are currently not aware of any issues with this update. For the most up-to-date information about known issues for Windows Server 2008 R2 SP1, please go to the Windows release health dashboard .
Writing about KB5055561? Cite this page
Copy-paste for a blog post, forum answer, or internal doc. The link always carries the current risk data.
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.
Affected products
Also released in April 2025
The highest-risk updates from the same release:
The full month, summarized: Microsoft Patch Tuesday.
How to install KB5055561
Any of these paths delivers KB5055561; most organizations already have one of the first three running:
- Intune update rings (Windows Update for Business): the update flows on each ring's deferral schedule. For this update, consider an expedite policy: it bypasses deferrals for exactly this fix-now case.
- Windows Autopatch: rings, rollout, and pause or rollback are managed for you; exploited updates can be expedited.
- WSUS / Configuration Manager: approve KB5055561 for your device groups and set a deadline (deadline, not just approval, for an exploited fix).
- Manual: download from the Update Catalog above and install; fine for a handful of machines, unmanageable at any real scale.
After the rollout, verify rather than assume: update compliance reporting in Intune or Autopatch shows which devices actually installed it, and Siemserva reads Intune, Defender, Autopatch, and Azure Update Manager together to show the devices still missing KB5055561, ranked by exploitation.
Common questions about KB5055561
Does KB5055561 have known issues?
Yes. Microsoft's support article documents known issues for KB5055561 (checked 2026-07-22). The Known issues section on this page quotes it; verify against the article before acting.
Is KB5055561 urgent?
Yes. KB5055561 fixes at least one vulnerability in the CISA Known Exploited Vulnerabilities catalog, meaning attackers are using it in the wild, including in ransomware campaigns. Deploy it first.
How do I download KB5055561?
From the Microsoft Update Catalog (linked on this page), or let Intune, Windows Update for Business, Windows Autopatch, or WSUS deliver it. The catalog page lists the download for each supported product.
How do I deploy KB5055561 with Intune?
Assign a Windows Update ring (quality update policy) to the device groups and the update flows on the ring's deferral schedule. Because KB5055561 fixes an actively exploited CVE, an Intune expedite policy is the right tool: it bypasses configured deferrals and pushes the update as soon as devices check in. Verify the rollout with update compliance reporting rather than assuming delivery.
Can I ask my own AI about KB5055561?
Yes. This page includes a free, ready-to-paste AI prompt containing KB5055561's key facts: severity, CVE count, exploitation status, and the download link. Copy it into Claude, ChatGPT, or Copilot for a rollout plan; the data is refreshed three times a day (5 AM, 12:30 PM, and 7 PM US Central).
Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.
