CVE-2026-55040

critical Microsoft ⚠️ CISA KEV — Exploited in the Wild
CVSS v3 Base Score
9.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS Score
4.0%
Exploitation probability in 30 days
Top 10% most likely to be exploited
Attack Characteristics
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Confidentiality
High
Integrity
High
Availability
None
Published: July 14, 2026 (54 days ago)
Last Modified: August 19, 2026
Vendor: Microsoft
Source: NVD

⚠️ CISA Known Exploited Vulnerability

Added to KEV: 2026-08-18
Remediation Due: 2026-08-21 (⚠ 17d overdue)

Description

Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.

CWE

CWE-1390

Affected Products

microsoft sharepoint server

References

🔗 msrc.microsoft.com 🔗 github.com 🔗 www.cisa.gov 🔗 www.rapid7.com