# KB5008263: December 2021 security update

KB5008263, released December 14, 2021, fixes 20 CVEs across 5 products. One of them is being exploited (CVE-2021-43226); 1 on CISA KEV. Patch Radar priority: Patch now.

- Web page: https://patchblox.com/security/fix/microsoft/kb5008263
- Platform: Microsoft
- Released: Dec 14, 2021
- Priority: Patch now (Closes CVE-2021-43226, exploited (CISA KEV, ransomware))
- CVEs: 20, exploited: 1, on CISA KEV: 1
- Vendor advisory: https://support.microsoft.com/help/5008263

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [Windows 8.1 for 32-bit systems](https://patchblox.com/security/data/product/microsoft/windows-8.1-for-32-bit-systems.md) |  |  |
| [Windows 8.1 for x64-based systems](https://patchblox.com/security/data/product/microsoft/windows-8.1-for-x64-based-systems.md) |  |  |
| [Windows RT 8.1](https://patchblox.com/security/data/product/microsoft/windows-rt-8.1.md) |  |  |
| [Windows Server 2012 R2](https://patchblox.com/security/data/product/microsoft/windows-server-2012-r2.md) |  |  |
| [Windows Server 2012 R2 (Server Core installation)](https://patchblox.com/security/data/product/microsoft/windows-server-2012-r2-server-core-installation.md) |  |  |

## CVEs this fix closes

| CVE | Priority | Component | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2021-43226](https://patchblox.com/security/data/cve/CVE-2021-43226.md) | Patch now | Windows Common Log File System Driver | 7.8 | 0.0328 | CISA KEV, Ransomware |
| [CVE-2021-43883](https://patchblox.com/security/data/cve/CVE-2021-43883.md) | Urgent | Windows Installer | 7.8 | 0.1215 | Disclosed |
| [CVE-2021-43217](https://patchblox.com/security/data/cve/CVE-2021-43217.md) | Urgent | Windows Encrypting File System (EFS) | 8.1 | 0.0652 |  |
| [CVE-2021-43215](https://patchblox.com/security/data/cve/CVE-2021-43215.md) | Urgent | Internet Storage Name Service | 9.8 | 0.0287 | More likely |
| [CVE-2021-43233](https://patchblox.com/security/data/cve/CVE-2021-43233.md) | Urgent | Remote Desktop Client | 7.5 | 0.0236 | More likely |
| [CVE-2021-41333](https://patchblox.com/security/data/cve/CVE-2021-41333.md) | Urgent | Windows Print Spooler Components | 7.8 | 0.0108 | Disclosed |
| [CVE-2021-43207](https://patchblox.com/security/data/cve/CVE-2021-43207.md) | Urgent | Windows Common Log File System Driver | 7.8 | 0.0068 | More likely |
| [CVE-2021-43893](https://patchblox.com/security/data/cve/CVE-2021-43893.md) | High | Windows Encrypting File System (EFS) | 7.5 | 0.0672 | Disclosed |
| [CVE-2021-43222](https://patchblox.com/security/data/cve/CVE-2021-43222.md) | High | Windows Message Queuing | 7.5 | 0.0317 |  |
| [CVE-2021-43236](https://patchblox.com/security/data/cve/CVE-2021-43236.md) | High | Windows Message Queuing | 7.5 | 0.0317 |  |
| [CVE-2021-43232](https://patchblox.com/security/data/cve/CVE-2021-43232.md) | High | Windows Event Tracing | 7.8 | 0.0218 |  |
| [CVE-2021-43234](https://patchblox.com/security/data/cve/CVE-2021-43234.md) | High | Role: Windows Fax Service | 7.8 | 0.0218 |  |
| [CVE-2021-43229](https://patchblox.com/security/data/cve/CVE-2021-43229.md) | High | Windows NTFS | 7.8 | 0.0179 |  |
| [CVE-2021-43238](https://patchblox.com/security/data/cve/CVE-2021-43238.md) | High | Windows Remote Access Connection Manager | 7.8 | 0.0091 |  |
| [CVE-2021-40441](https://patchblox.com/security/data/cve/CVE-2021-40441.md) | High | Windows Media | 7.8 | 0.0072 |  |
| [CVE-2021-43230](https://patchblox.com/security/data/cve/CVE-2021-43230.md) | High | Windows NTFS | 7.8 | 0.0057 |  |
| [CVE-2021-43223](https://patchblox.com/security/data/cve/CVE-2021-43223.md) | High | Windows Remote Access Connection Manager | 7.8 | 0.0054 |  |
| [CVE-2021-43248](https://patchblox.com/security/data/cve/CVE-2021-43248.md) | High | Microsoft Windows Codecs Library | 7.8 | 0.0054 |  |
| [CVE-2021-43224](https://patchblox.com/security/data/cve/CVE-2021-43224.md) | Routine | Windows Common Log File System Driver | 5.5 | 0.0393 |  |
| [CVE-2021-43216](https://patchblox.com/security/data/cve/CVE-2021-43216.md) | Routine | Microsoft Local Security Authority Server (lsasrv) | 6.5 | 0.0343 |  |

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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