Actively exploited in the wild
Microsoft SharePoint Weak Authentication Vulnerability
Microsoft - SharePoint · Listed in the CISA KEV since 2026-08-18. This indicates confirmed attacks in production environments.
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.
CVE-2026-55040
CriticalCVSS 9.1KEVExploitation Probability (EPSS)
Very high risk92th percentile - higher than 92% of all known CVEs
Summary
A vulnerability in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over the network due to weak authentication.
Risk Assessment
An attacker can gain unauthorized access to SharePoint data and functionality, leading to a breach of confidentiality and integrity of organizational information.
Recommendation
Apply the latest security updates provided by Microsoft for SharePoint and enable stronger authentication mechanisms such as multi-factor authentication.
Other vulnerabilities in Microsoft Office SharePoint
See all- CVE-2026-40368High
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
- CVE-2026-40357High
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
- CVE-2026-35439High
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
- CVE-2026-33112High
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
- CVE-2026-33110High
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
- CVE-2026-20951High
Improper input validation in Microsoft Office SharePoint allows an unauthorized attacker to execute code locally.
- CVE-2026-20947High
Improper neutralization of special elements used in an sql command ('sql injection') in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
- CVE-2026-70306Critical
A cross-site scripting vulnerability in Microsoft Office SharePoint allows an unauthorized attacker to perform spoofing over a network.
- CVE-2026-70332Critical
Improper input neutralization during web page generation (cross-site scripting) in Microsoft Office SharePoint allows an unauthorized attacker to perform spoofing over a network.
- CVE-2026-58644CriticalActively exploited
A deserialization of untrusted data vulnerability in Microsoft Office SharePoint allows an unauthorized attacker to execute code remotely over a network.
Original NVD description (English source)
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.