Patch tracker / KB5091596

KB5091596

Microsoft security update released 2026-04-14. Fixes 1 CVE.

Critical

Download KB5091596

Get the official update for KB5091596. The download and file size for each supported product are on the Microsoft Update Catalog page.

Microsoft Update Catalog: download KB5091596Microsoft support article

Update summary

Released
2026-04-14
CVEs fixed
1
Max CVSS
9.1
Severity
Critical

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.

CVEs fixed by this update

CVE-2026-40372

Affected products

  • ASP.NET Core 10.0

References

Microsoft support articleMicrosoft Security Update Guide

See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.

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Lexicon: the terms on this page
CVE
Common Vulnerabilities and Exposures. A unique ID for one publicly known vulnerability, such as CVE-2025-1234.
KB
Microsoft Knowledge Base article. The identifier for a specific Microsoft update.
KEV
CISA Known Exploited Vulnerabilities. CVEs confirmed exploited in the wild. Fix these first.
CVSS
Common Vulnerability Scoring System. A standardized Severity score from 0 to 10.
EPSS
Exploit Prediction Scoring System. The probability a CVE will be exploited in the next 30 days.
MSRC
Microsoft Security Response Center. Microsoft's Patch Tuesday advisories and KB-to-CVE mapping.
NVD
National Vulnerability Database (NIST). Authoritative CVE metadata and CVSS scores.
Ransomware
The vulnerability is linked to known ransomware activity.