Snapshot of public data from 31 Oct 2026, 12:50:06. This data is not updated until the API is deployed.

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CVE-2026-55040

Microsoft SharePoint Weak Authentication Vulnerability

UrgentCVSS 9.1 v3.1Exploited

Why this priority

?

Generic watch priority computed by public, versioned rules. It does not know your assets. See the glossary

  • Présent dans le catalogue CISA KEV (exploitation confirmée)

Description

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

Affected products

VendorProductVersions
MicrosoftMicrosoft SharePoint Enterprise Server 2016
  • from 16.0.0 to 16.0.5561.1001 excluded
MicrosoftMicrosoft SharePoint Server 2019
  • from 16.0.0 to 16.0.10417.20175 excluded
MicrosoftMicrosoft SharePoint Server Subscription Edition
  • from 16.0.0 to 16.0.19725.20434 excluded
MicrosoftSharePointAll versions

Revision history

  1. Revision 3

  2. Revision 2

    Update : Affected versions changed

  3. Revision 1

    New record

Qualification

CVSS severity
?

Technical severity score between 0 and 10, with its version (3.1, 4.0). See the glossary

9.1 CRITICAL CVSS v3.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C
KEV catalog
?

CISA catalog of vulnerabilities with confirmed exploitation. Absence from the catalog does not prove absence of exploitation. See the glossary

Listed
Exploitation
Confirmed
EPSS probability
?

Probability, between 0 and 1, that a vulnerability is exploited in the next 30 days, published daily by FIRST. Always dated. See the glossary

Unknown
Confidence
?

Quality of the sources behind the record. It is not a risk score. See the glossary

High

Priority rules, version 1

CISA KEV catalog

Added on
18 August 2026
Federal due date
21 August 2026
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.
Ransomware use
Unknown

Record

Published on
14 July 2026
Weaknesses (CWE)
CWE-1390

Sources

References

CVE-2026-55040 Microsoft SharePoint Weak Authentication Vulnerability · Avanguard TACTIC