Patch tracker / KB5091596
KB5091596: ASP.NET Core 10.0 Security Update (April 2026)
KB5091596 is a Critical security update for ASP.NET Core 10.0, released 2026-04-14. It closes 1 CVE with a maximum CVSS of 9.1. Get it from the Microsoft Update Catalog below, and see where it sits against the rest of the month on the patch tracker.
Update summary
New to these terms? How the Microsoft patching tools fit together, this month's Patch Tuesday summary, and every update ranked by real-world risk.
Senserva AI Opinion for KB5091596
KB5091596 patches CVE-2026-40372 in ASP.NET Core 10.0, rated Critical at CVSS 9.1, so any server or app running this framework version is exposed. The EPSS score of 11 percent is elevated for a fresh release and suggests exploitation is more plausible than typical, though it is not yet in CISA KEV or tied to ransomware. Because ASP.NET Core often powers internet-facing web APIs and sites, a Critical flaw here can reach externally accessible surfaces.
Do this: Inventory hosts running ASP.NET Core 10.0 and deploy KB5091596 to internet-facing web servers first.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5091596
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5091596
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 1 CVE. Most severe CVSS 9.1 (Critical). EPSS exploit probability up to 11%.
Among the top half of tracked Microsoft updates by EPSS exploit probability.
What to do
Elevated priority: high severity or a meaningful exploitation probability, sooner if an affected product is internet-facing. Senserva flags whether KB5091596 is missing on your devices.
Check if KB5091596 is installed
Copy-paste PowerShell: one machine, or your whole estate 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.
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-2026-40372 | Critical | 9.1 | 11% | No |
Affected products
Also released in April 2026
The highest-risk updates from the same release:
The full month, summarized: Microsoft Patch Tuesday.
Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.