# KB5071875: December 2025 security update

KB5071875, released December 9, 2025, fixes 2 CVEs in Microsoft Exchange Server 2019 Cumulative Update 15. None of them is reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/fix/microsoft/kb5071875
- Platform: Microsoft
- Released: Dec 9, 2025
- Priority: High (Closes CVE-2025-64666, high severity)
- CVEs: 2, exploited: 0, on CISA KEV: 0
- Vendor advisory: https://support.microsoft.com/help/5071875

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [Microsoft Exchange Server 2019 Cumulative Update 15](https://patchblox.com/security/data/product/microsoft/microsoft-exchange-server-2019-cumulative-update-15.md) |  |  |

## CVEs this fix closes

| CVE | Priority | Component | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2025-64666](https://patchblox.com/security/data/cve/CVE-2025-64666.md) | High | Microsoft Exchange Server | 7.5 | 0.0102 |  |
| [CVE-2025-64667](https://patchblox.com/security/data/cve/CVE-2025-64667.md) | Routine | Microsoft Exchange Server | 5.3 | 0.0080 |  |

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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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo