CVE-2026-55040
Microsoft SharePoint Server Security Feature Bypass Vulnerability
At a glance
- Severity
- CRITICAL 9.1
- Exploitation
- Known exploited (CISA KEV) · added 2026-08-18
Exploited per ENISA since 2026-08-18 - EPSS
- EPSS 69.54 % · percentile 99 (2026-10-27)
- State
- PUBLISHED
- Published
- Updated
- Assigner
- microsoft
- NVD status
- Analyzed
Description
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | CRITICAL 9.1 | 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 | microsoft |
| CVSS 3.1 | CRITICAL 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | NVD · secure@microsoft.com (Secondary) |
Weaknesses (CWE)
European references
- ENISA EUVD · EUVD-2026-44211
- GCVE · GCVE-0-2026-55040
CERT-FR advisories
- CERTFR-2026-AVI-0872 — Multiples vulnérabilités dans les produits Microsoft · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:microsoft:sharepoint_server:*:*:*:*:subscription:*:*:*< 16.0.19725.20434cpe:2.3:a:microsoft:sharepoint_server:2016:*:*:*:enterprise:*:*:*cpe:2.3:a:microsoft:sharepoint_server:2019:*:*:*:*:*:*:*
Affected products
| Product | Versions |
|---|---|
| Microsoft · Microsoft SharePoint Enterprise Server 2016 | affected 16.0.0 < 16.0.5561.1001 |
| Microsoft · Microsoft SharePoint Server 2019 | affected 16.0.0 < 16.0.10417.20175 |
| Microsoft · Microsoft SharePoint Server Subscription Edition | affected 16.0.0 < 16.0.19725.20434 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040
- https://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/
- https://github.com/sfewer-r7/CVE-2026-55040
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| CISA Known Exploited Vulnerabilities | CC0 1.0 |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |