# KB5129958: October 2026 security update

KB5129958, released October 2, 2026, fixes 1 CVE in Microsoft Exchange Server 2016 Cumulative Update 23. None of them is reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/fix/microsoft/kb5129958
- Platform: Microsoft
- Released: Oct 2, 2026
- Priority: Urgent (Closes CVE-2026-96940, exploitation more likely)
- CVEs: 1, exploited: 0, on CISA KEV: 0
- Vendor advisory: https://support.microsoft.com/help/5129958

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [Microsoft Exchange Server 2016 Cumulative Update 23](https://patchblox.com/security/data/product/microsoft/microsoft-exchange-server-2016-cumulative-update-23.md) |  |  |

## CVEs this fix closes

| CVE | Priority | Component | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2026-96940](https://patchblox.com/security/data/cve/CVE-2026-96940.md) | Urgent | Microsoft Exchange Server | 8.8 | 0.0275 | More likely |

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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo