# KB4534978: January 2020 security update

KB4534978, released January 14, 2020, fixes 3 CVEs across 16 products. One of them is being exploited (CVE-2020-0646); 1 on CISA KEV. Patch Radar priority: Patch now.

- Web page: https://patchblox.com/security/fix/microsoft/kb4534978
- Platform: Microsoft
- Released: Jan 14, 2020
- Priority: Patch now (Closes CVE-2020-0646, exploited (CISA KEV))
- CVEs: 3, exploited: 1, on CISA KEV: 1
- Vendor advisory: https://support.microsoft.com/help/4534978

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [Microsoft .NET Framework 3.5 on Windows 8.1 for 32-bit systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-3.5-on-windows-8.1-for-32-bit-systems.md) |  |  |
| [Microsoft .NET Framework 3.5 on Windows 8.1 for x64-based systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-3.5-on-windows-8.1-for-x64-based-systems.md) |  |  |
| [Microsoft .NET Framework 3.5 on Windows Server 2012 R2](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-3.5-on-windows-server-2012-r2.md) |  |  |
| [Microsoft .NET Framework 3.5 on Windows Server 2012 R2 (Server Core installation)](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-3.5-on-windows-server-2012-r2-server-core-installation.md) |  |  |
| [Microsoft .NET Framework 4.5.2 on Windows 8.1 for 32-bit systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.5.2-on-windows-8.1-for-32-bit-systems.md) |  |  |
| [Microsoft .NET Framework 4.5.2 on Windows 8.1 for x64-based systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.5.2-on-windows-8.1-for-x64-based-systems.md) |  |  |
| [Microsoft .NET Framework 4.5.2 on Windows Server 2012 R2](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.5.2-on-windows-server-2012-r2.md) |  |  |
| [Microsoft .NET Framework 4.5.2 on Windows Server 2012 R2 (Server Core installation)](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.5.2-on-windows-server-2012-r2-server-core-installation.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 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 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) |  |  |
| [Microsoft .NET Framework 4.8 on Windows 8.1 for 32-bit systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.8-on-windows-8.1-for-32-bit-systems.md) |  |  |
| [Microsoft .NET Framework 4.8 on Windows 8.1 for x64-based systems](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.8-on-windows-8.1-for-x64-based-systems.md) |  |  |
| [Microsoft .NET Framework 4.8 on Windows Server 2012 R2](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.8-on-windows-server-2012-r2.md) |  |  |
| [Microsoft .NET Framework 4.8 on Windows Server 2012 R2 (Server Core installation)](https://patchblox.com/security/data/product/microsoft/microsoft-.net-framework-4.8-on-windows-server-2012-r2-server-core-installation.md) |  |  |

## CVEs this fix closes

| CVE | Priority | Component | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2020-0646](https://patchblox.com/security/data/cve/CVE-2020-0646.md) | Patch now | .NET Framework | n/a | 0.9922 | CISA KEV |
| [CVE-2020-0605](https://patchblox.com/security/data/cve/CVE-2020-0605.md) | Urgent | .NET Framework | n/a | 0.1840 |  |
| [CVE-2020-0606](https://patchblox.com/security/data/cve/CVE-2020-0606.md) | Urgent | .NET Framework | n/a | 0.1834 |  |

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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