# KB4457034: September 2018 security update

KB4457034, released September 12, 2018, fixes 1 CVE across 5 products. None of them is reported as exploited. Patch Radar priority: Urgent. The product is no longer supported.

- Web page: https://patchblox.com/security/fix/microsoft/kb4457034
- Platform: Microsoft
- Released: Sep 12, 2018
- Priority: Urgent (Closes CVE-2018-8421, rated Critical)
- CVEs: 1, exploited: 0, on CISA KEV: 0
- Vendor advisory: https://support.microsoft.com/help/4457034

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2 on Windows 8.1 for 32-bit systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.6-4.6.1-4.6.2-4.7-4.7.1-4.7.2-on-windows-8.1-for-32-bit-systems.md) |  |  |
| [Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2 on Windows 8.1 for x64-based systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.6-4.6.1-4.6.2-4.7-4.7.1-4.7.2-on-windows-8.1-for-x64-based-systems.md) |  |  |
| [Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2 on Windows RT 8.1](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.6-4.6.1-4.6.2-4.7-4.7.1-4.7.2-on-windows-rt-8.1.md) |  |  |
| [Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 R2](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.6-4.6.1-4.6.2-4.7-4.7.1-4.7.2-on-windows-server-2012-r2.md) |  |  |
| [Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 R2 (Server Core installation)](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.6-4.6.1-4.6.2-4.7-4.7.1-4.7.2-on-windows-server-2012-r2-server-core-installation.md) |  |  |

## CVEs this fix closes

| CVE | Priority | Component | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2018-8421](https://patchblox.com/security/data/cve/CVE-2018-8421.md) | Urgent | .NET Framework | n/a | 0.2908 |  |

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Data as of 2026-11-07T06:34:28Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo