CVSS 3.1
9.1 criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NCVE-2026-55040
Critical (9.1) in Microsoft SharePoint. In CISA KEV since 2026-08-18. EPSS 70% chance of exploitation in the next 30 days.
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
Severity
- EPSS
- 70% chance of exploitation in the next 30 days; higher than 99% of CVEs (scores of 2026-10-31)
- CISA KEV
- listed 2026-08-18, due 2026-08-21
- CWE
- CWE-1390
- Published
- Modified
- Record from
- the NVD, synced
Affected
- microsoft:sharepoint_server
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040
- https://github.com/sfewer-r7/CVE-2026-55040
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040
- https://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/