# KB5091596: April 2026 security update

KB5091596, released April 21, 2026, fixes 1 CVE in ASP.NET Core 10.0. None of them is reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/fix/microsoft/kb5091596
- Platform: Microsoft
- Released: Apr 21, 2026
- Priority: High (Closes CVE-2026-40372, high severity)
- CVEs: 1, exploited: 0, on CISA KEV: 0
- Vendor advisory: https://support.microsoft.com/help/5091596

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [ASP.NET Core 10.0](https://patchblox.com/security/data/product/microsoft/asp.net-core-10.0.md) |  |  |

## CVEs this fix closes

| CVE | Priority | Component | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2026-40372](https://patchblox.com/security/data/cve/CVE-2026-40372.md) | High | ASP.NET Core | 9.1 | 0.1121 |  |

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Data as of 2026-11-07T12:40:37Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo