# CVE-2026-55040: Microsoft SharePoint Server Security Feature Bypass Vulnerability

CVE-2026-55040 is fixed in 3 products on 1 platform, first by KB5002891, released July 14, 2026. It is being exploited: CISA added it to the Known Exploited Vulnerabilities catalog on August 18, 2026. Patch Radar priority: Patch now.

- Web page: https://patchblox.com/security/cve/CVE-2026-55040
- Priority: Patch now
- CVSS: 9.1 (Critical)
- EPSS: 0.6954
- CISA KEV: listed Aug 18, 2026, federal due date Aug 21, 2026
- Exploited (vendor report): no
- Publicly disclosed: no
- Vendor exploitability assessment: Exploitation More Likely
- Published: Jul 14, 2026
- Weakness: Weak Authentication
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040

## Description

<p>Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.</p>

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Microsoft | Microsoft SharePoint Enterprise Server 2016 |  | [KB5002891](https://patchblox.com/security/data/fix/microsoft/kb5002891.md) | Jul 14, 2026 |
| Microsoft | Microsoft SharePoint Server 2019 |  | [KB5002883](https://patchblox.com/security/data/fix/microsoft/kb5002883.md) | Jul 14, 2026 |
| Microsoft | Microsoft SharePoint Server Subscription Edition |  | [KB5002882](https://patchblox.com/security/data/fix/microsoft/kb5002882.md) | Jul 14, 2026 |

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Data as of 2026-11-08T06:59:42Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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