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

criticalCVSS 9.1CVE-2026-55040
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.

CSIRTS triage

vendor: Microsoftproduct: Microsoft SharePoint ServerAuthentication bypass
What
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
Who is affected
Deployments of Microsoft Office SharePoint.
Urgency
Remediation is critical due to the high severity and potential for unauthorized access.
Action
Apply the latest security patch for Microsoft SharePoint Server.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
critical — CVSS 9.1
Published
2026-07-14
Exploitation
Not in CISA KEV at last sync

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

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-55040coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Microsoft SharePoint Server

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

More from Microsoft Security Response Center