CVE-2026-55040: Microsoft SharePoint Weak Authentication Vulnerability

Required action (CISA's text)

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.

Description (NVD)

Microsoft SharePoint contains a weak authentication vulnerability which allows an unauthorized attacker to bypass a security feature over a network.

SOURCES

• CISA KEVCISA Known Exploited Vulnerabilities catalog

Other Microsoft flaws

• patchtuesday:2026-11: Vulnerability in Microsoft
• CVE-2026-124194: Microsoft Office Outlook Missing User Interaction for Potentially Unsafe Action Vulnerability
• CVE-2026-96951: Microsoft Windows Command Injection Vulnerability
• CVE-2026-65660: Microsoft SharePoint Code Injection Vulnerability
• CVE-2026-85880: Microsoft Windows Heap-Based Buffer Overflow Vulnerability

Data from NVD, CISA KEV, FIRST EPSS and vendor advisories. Updated 10 Nov 2026.