August 18, 2026 · Applied Cybernetics Group
CVE-2026-55040 — Microsoft SharePoint
Microsoft SharePoint Weak Authentication Vulnerability
- Added to KEV
2026-08-18- Federal due date
2026-08-21- Vendor
- Microsoft
- Product
- SharePoint
- EPSS
- 98.9th percentile (score 0.506, as of
2026-09-16) - NVD CVSS v3.1
- 9.1 (CRITICAL)
- Ransomware use
- Unknown
- Upstream
- https://nvd.nist.gov/vuln/detail/CVE-2026-55040
CISA short description
Microsoft SharePoint contains a weak authentication vulnerability which allows an unauthorized attacker to bypass a security feature over a network.
Required action
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.
NVD description
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.