# KB4040956: September 2017 security update

KB4040956, released September 12, 2017, fixes 1 CVE across 4 products. One of them is being exploited (CVE-2017-8759); 1 on CISA KEV. Patch Radar priority: Patch now. The product is no longer supported.

- Web page: https://patchblox.com/security/fix/microsoft/kb4040956
- Platform: Microsoft
- Released: Sep 12, 2017
- Priority: Patch now (Closes CVE-2017-8759, exploited (CISA KEV))
- CVEs: 1, exploited: 1, on CISA KEV: 1
- Vendor advisory: https://support.microsoft.com/help/4040956

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7 on Windows 8.1 for 32-bit systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.6-4.6.1-4.6.2-4.7-on-windows-8.1-for-32-bit-systems.md) |  |  |
| [Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7 on Windows 8.1 for x64-based systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.6-4.6.1-4.6.2-4.7-on-windows-8.1-for-x64-based-systems.md) |  |  |
| [Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7 on Windows Server 2012 R2](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.6-4.6.1-4.6.2-4.7-on-windows-server-2012-r2.md) |  |  |
| [Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7 on Windows Server 2012 R2 (Server Core installation)](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.6-4.6.1-4.6.2-4.7-on-windows-server-2012-r2-server-core-installation.md) |  |  |

## CVEs this fix closes

| CVE | Priority | Component | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2017-8759](https://patchblox.com/security/data/cve/CVE-2017-8759.md) | Patch now | .NET Framework | n/a | 0.8870 | CISA KEV |

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Data as of 2026-11-07T18:46:35Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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