# KB5000800: March 2021 security update

KB5000800, released March 9, 2021, fixes 1 CVE across 9 products. One of them is being exploited (CVE-2021-26411); 1 on CISA KEV. Patch Radar priority: Patch now. The product is no longer supported.

- Web page: https://patchblox.com/security/fix/microsoft/kb5000800
- Platform: Microsoft
- Released: Mar 9, 2021
- Priority: Patch now (Closes CVE-2021-26411, exploited (CISA KEV, ransomware))
- CVEs: 1, exploited: 1, on CISA KEV: 1
- Vendor advisory: https://support.microsoft.com/help/5000800

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [Internet Explorer 11 on Windows 7 for 32-bit Systems Service Pack 1](https://patchblox.com/security/data/product/microsoft/internet-explorer-11-on-windows-7-for-32-bit-systems-service-pack-1.md) |  |  |
| [Internet Explorer 11 on Windows 7 for x64-based Systems Service Pack 1](https://patchblox.com/security/data/product/microsoft/internet-explorer-11-on-windows-7-for-x64-based-systems-service-pack-1.md) |  |  |
| [Internet Explorer 11 on Windows 8.1 for 32-bit systems](https://patchblox.com/security/data/product/microsoft/internet-explorer-11-on-windows-8.1-for-32-bit-systems.md) |  |  |
| [Internet Explorer 11 on Windows 8.1 for x64-based systems](https://patchblox.com/security/data/product/microsoft/internet-explorer-11-on-windows-8.1-for-x64-based-systems.md) |  |  |
| [Internet Explorer 11 on Windows Server 2008 R2 for x64-based Systems Service Pack 1](https://patchblox.com/security/data/product/microsoft/internet-explorer-11-on-windows-server-2008-r2-for-x64-based-systems-service-pack-1.md) |  |  |
| [Internet Explorer 11 on Windows Server 2012](https://patchblox.com/security/data/product/microsoft/internet-explorer-11-on-windows-server-2012.md) |  |  |
| [Internet Explorer 11 on Windows Server 2012 R2](https://patchblox.com/security/data/product/microsoft/internet-explorer-11-on-windows-server-2012-r2.md) |  |  |
| [Internet Explorer 9 on Windows Server 2008 for 32-bit Systems Service Pack 2](https://patchblox.com/security/data/product/microsoft/internet-explorer-9-on-windows-server-2008-for-32-bit-systems-service-pack-2.md) |  |  |
| [Internet Explorer 9 on Windows Server 2008 for x64-based Systems Service Pack 2](https://patchblox.com/security/data/product/microsoft/internet-explorer-9-on-windows-server-2008-for-x64-based-systems-service-pack-2.md) |  |  |

## CVEs this fix closes

| CVE | Priority | Component | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2021-26411](https://patchblox.com/security/data/cve/CVE-2021-26411.md) | Patch now | Internet Explorer | 8.8 | 0.8167 | CISA KEV, Ransomware, Disclosed |

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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

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