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CVE-2026-55040Microsoft SharePoint Server Security Feature Bypass Vulnerability
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
9.1 CRITICALEPSS 69.53%⚡ Known Exploited (CISA KEV)NVD: Analyzed
Overview
Severity
| Score | Severity | Version | Vector String |
|---|---|---|---|
| 9.1 | CRITICAL | 3.1microsoft (CNA) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
| 9.1 | CRITICAL | 3.1microsoft (CNA) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C |
CISA required action
⚡ Known exploited · remediation due Aug 21, 2026
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Details
- CVE ID
- CVE-2026-55040
- Status
- Analyzed
- Assigner (CNA)
- microsoft
- Published
- Jul 14, 2026
- Last modified
- 2026-11-01 17:36 UTC
- Weaknesses
- CWE-1390 · Weak Authentication
Affected Products
As published by the CNA in the CVE record.
MicrosoftMicrosoft SharePoint Enterprise Server 20161 version range
- 16.0.0 before 16.0.5561.1001
MicrosoftMicrosoft SharePoint Server 20191 version range
- 16.0.0 before 16.0.10417.20175
MicrosoftMicrosoft SharePoint Server Subscription Edition1 version range
- 16.0.0 before 16.0.19725.20434
References
- msrc.microsoft.com https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040
- github.com https://github.com/sfewer-r7/CVE-2026-55040
- cisa.gov https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040
- rapid7.com https://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/