CVE-2026-55040

Microsoft SharePoint Server Security Feature Bypass Vulnerability

CVSS 3.1 Critical 9.1Known exploited (CISA KEV)

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

Description

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

Key data

CVSS 3.1 Critical 9.1

Score published by microsoft in the CVE record.

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

Attack vector: Network
The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity: Low
No special conditions are needed. The attack can be repeated at will.
Privileges required: None
No account or privileges are needed.
User interaction: None
No action from any user is needed.
Scope: Unchanged
The impact stays within the vulnerable component.
Confidentiality impact: High
Serious or total effect on the secrecy of data.
Integrity impact: High
Serious or total effect on the trustworthiness of data.
Availability impact: None
No effect on availability.

Metric	Value	What it means
Attack vector	Network	The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity	Low	No special conditions are needed. The attack can be repeated at will.
Privileges required	None	No account or privileges are needed.
User interaction	None	No action from any user is needed.
Scope	Unchanged	The impact stays within the vulnerable component.
Confidentiality impact	High	Serious or total effect on the secrecy of data.
Integrity impact	High	Serious or total effect on the trustworthiness of data.
Availability impact	None	No effect on availability.

CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at first.org/cvss.

EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.

Score: 0.69536 (69.5% probability)
Percentile: 99.4%
Scores of: Nov 10, 2026
Model: v2026.06.15

CISA Known Exploited Vulnerabilities

This CVE is listed in the CISA KEV catalog.

Name in the catalog: Microsoft SharePoint Weak Authentication Vulnerability
Added to the catalog: Aug 18, 2026
Federal due date: Aug 21, 2026

CISA assessment as of Jul 13, 2026

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.

Exploitation: Recorded by CISA as active
Automatable: yes
Technical impact: total

Weakness (CWE)

CWE catalog version 5.0.

CWE-1390Weak Authentication

Affected products

Products listed in the CVE record, as the CNA published them.

Microsoft SharePoint Enterprise Server 2016
- affected: 16.0.0 up to before 16.0.5561.1001
Microsoft SharePoint Server 2019
- affected: 16.0.0 up to before 16.0.10417.20175
Microsoft SharePoint Server Subscription Edition
- affected: 16.0.0 up to before 16.0.19725.20434

References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

Microsoft SharePoint Server Security Feature Bypass Vulnerability (msrc.microsoft.com)vendor-advisorypatch

Timeline

ID reservedJun 16, 2026
Record publishedJul 14, 2026
Added to CISA KEVAug 18, 2026
Record last updatedNov 1, 2026

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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:09 UTC. Sources and licenses