CVE-2026-55040

Analyzed

Published: 14 Jul 2026, 17:09

Last modified:19 Aug 2026, 16:30

Vulnerability Summary

Overall Risk (default)

high

70/100

CVSS Score

9.1 CRITICAL

v3.1 (cve.org)

EPSS Score

5.49% LOW

5% probability +1.52%

KEV

Listed

CISA

1 listing

Ransomware

No reports

Public exploits

2 found

Dark Web

Not detected

Timeline

14 Jul 2026, 17:09

Published

Vulnerability first disclosed

18 Aug 2026, 00:00

Added to CISA KEV

Microsoft SharePoint Weak Authentication Vulnerability

19 Aug 2026, 16:30

Last Modified

Vulnerability information updated

21 Aug 2026, 00:00

CISA Remediation Due

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.

Description

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

CVSS Metrics

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

EPSS Trends

Current EPSS score: 5.49%• Percentile: 92%

Techniques & Countermeasures

CWE-1390•Weak Authentication
The product uses an authentication mechanism to restrict access to specific users or identities, but the mechanism does not sufficiently prove that the claimed identity is correct.

Affected Systems

microsoft•microsoft sharepoint enterprise server 2016
≥ 16.0.0, < 16.0.5561.1001
microsoft•microsoft sharepoint server 2019
≥ 16.0.0, < 16.0.10417.20175
microsoft•microsoft sharepoint server subscription edition
≥ 16.0.0, < 16.0.19725.20434
microsoft•sharepoint_server
< 16.0.19725.20434 | 2016 | 2019