CVE-2026-55040Microsoft SharePoint Server Security Feature Bypass Vulnerability

In plain English

A critical-severity security flaw in Microsoft SharePoint Enterprise Server 2016 from Microsoft. Attackers are actively exploiting it in the wild (listed by CISA on August 18, 2026). The chance it is exploited in the next 30 days is estimated at 69.5% (higher than 99.4% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei, public proof-of-concept code. 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.