CVE-2026-55040

CRITICALCVSS 9.1Known Exploited

CISA Known Exploited Vulnerability

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-55040

Remediation deadline: August 21, 2026

Description

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

Timeline

Published:July 14th, 2026 6:18 PM

Last modified:August 13th, 2026 5:17 AM

Added to KEV:August 18th, 2026

CVSS Scoring

CVSS v3: 9.1 (CRITICAL)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected Software

From NVD CPE configuration data

Vendors

microsoft

Products

sharepoint_server

Weaknesses (CWE)

CWE-1390

References & Reports

Advisories, patches, and third-party reports

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040Patch

Source: NIST NVD · Data may lag official sources by up to one minute