IRONSMITHINTEL
CRITICAL
|Auth: varies by cve|Reboot: required|Est. 30–60 minutes including reboot|Manual only

KB5055519: Windows Server 2019 Cumulative Update (May 2026)

The April 2026 cumulative update for Windows Server 2019 includes critical security fixes — unpatched servers are exposed to multiple actively exploited vulnerabilities.

Published May 7, 2026 · Updated May 10, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

Servers missing this update are exposed to all vulnerabilities addressed in the April 2026 patch cycle, which includes fixes for privilege escalation, remote code execution, and information disclosure vulnerabilities.

How the attack works

Microsoft's April 2026 Patch Tuesday includes the monthly cumulative update for Windows Server 2019 (KB5055519). This update bundles all previously released security fixes plus new patches for vulnerabilities discovered since the March 2026 update. Cumulative updates must be applied as a complete package.

Am I affected?Quick check

Probably yes if any of these apply:

●All Windows Server 2019 systems
●Running Windows Server 2019 prior to KB5055519

Affected OS versions

Windows Server 2019
Fixed inKB5055519
Real-world incidentsWhat we've seen

Organisations with delayed patch cycles are targeted specifically because attackers know there is a predictable window of vulnerability between patch release and deployment.

How to patch

Manual download

For air-gapped servers or out-of-band deployment. Microsoft Update Catalog returns every OS-version variant of this update.

↗ Microsoft Update CatalogKB5055519

Manual remediation steps

⏱ 30–60 minutes including reboot

Check if KB5055519 Is Installed

Get-HotFix -Id KB5055519
# No output means the patch is not installed

Apply via Windows Update

1
Open Settings → Windows Update
2
Click Check for updates
3
Install all available updates
4
Restart when prompted

Apply Manually

1
Download KB5055519 from Microsoft Update Catalog: catalog.update.microsoft.com
2
Run the MSU installer
3
Restart the server

Verification

Get-HotFix -Id KB5055519
# Must show the KB with an InstalledOn date
PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ MSRC Advisory↗ KBKB5055519