# KB5007255: November 2021 security update

KB5007255, released November 9, 2021, fixes 17 CVEs across 4 products. 3 of them are being exploited (CVE-2021-42287); 3 on CISA KEV. Patch Radar priority: Patch now.

- Web page: https://patchblox.com/security/fix/microsoft/kb5007255
- Platform: Microsoft
- Released: Nov 9, 2021
- Priority: Patch now (Closes CVE-2021-42287, exploited (CISA KEV, ransomware))
- CVEs: 17, exploited: 3, on CISA KEV: 3
- Vendor advisory: https://support.microsoft.com/help/5007255

## 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 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-2021-42287](https://patchblox.com/security/data/cve/CVE-2021-42287.md) | Patch now | Windows Active Directory | 7.5 | 0.7717 | CISA KEV, Ransomware |
| [CVE-2021-42278](https://patchblox.com/security/data/cve/CVE-2021-42278.md) | Patch now | Windows Active Directory | 7.5 | 0.7330 | CISA KEV, Ransomware |
| [CVE-2021-41379](https://patchblox.com/security/data/cve/CVE-2021-41379.md) | Patch now | Windows Installer | 5.5 | 0.1945 | CISA KEV, Ransomware |
| [CVE-2021-38666](https://patchblox.com/security/data/cve/CVE-2021-38666.md) | Urgent | Windows RDP | 8.8 | 0.1518 | More likely |
| [CVE-2021-38665](https://patchblox.com/security/data/cve/CVE-2021-38665.md) | High | Windows RDP | 7.4 | 0.0702 |  |
| [CVE-2021-42282](https://patchblox.com/security/data/cve/CVE-2021-42282.md) | High | Windows Active Directory | 7.5 | 0.0417 |  |
| [CVE-2021-42291](https://patchblox.com/security/data/cve/CVE-2021-42291.md) | High | Windows Active Directory | 7.5 | 0.0417 |  |
| [CVE-2021-42275](https://patchblox.com/security/data/cve/CVE-2021-42275.md) | High | Windows COM | 8.8 | 0.0210 |  |
| [CVE-2021-42285](https://patchblox.com/security/data/cve/CVE-2021-42285.md) | High | Windows Kernel | 7.8 | 0.0055 |  |
| [CVE-2021-42283](https://patchblox.com/security/data/cve/CVE-2021-42283.md) | High | Windows NTFS | 8.8 | 0.0049 |  |
| [CVE-2021-41366](https://patchblox.com/security/data/cve/CVE-2021-41366.md) | High | Windows Cred SSProvider Protocol | 7.8 | 0.0049 |  |
| [CVE-2021-41367](https://patchblox.com/security/data/cve/CVE-2021-41367.md) | High | Windows NTFS | 7.8 | 0.0049 |  |
| [CVE-2021-41370](https://patchblox.com/security/data/cve/CVE-2021-41370.md) | High | Windows NTFS | 7.8 | 0.0049 |  |
| [CVE-2021-41377](https://patchblox.com/security/data/cve/CVE-2021-41377.md) | High | Windows Fast FAT Driver | 7.8 | 0.0049 |  |
| [CVE-2021-42284](https://patchblox.com/security/data/cve/CVE-2021-42284.md) | Routine | Role: Windows Hyper-V | 6.8 | 0.0376 |  |
| [CVE-2021-38631](https://patchblox.com/security/data/cve/CVE-2021-38631.md) | Routine | Windows RDP | 4.4 | 0.0188 | Disclosed |
| [CVE-2021-41371](https://patchblox.com/security/data/cve/CVE-2021-41371.md) | Routine | Windows RDP | 4.4 | 0.0165 | Disclosed |

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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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