What is CVE-2026-20959?

CVE-2026-20959 is a medium-severity vulnerability in Microsoft Sharepoint Enterprise Server 2016, classified under Cross-site Scripting. CVSS score: 4.6/10. Published 2026-01-13.

How severe is CVE-2026-20959?

Medium severity. CVSS v3 base score is 4.6 out of 10.

XSS in Microsoft Sharepoint Enterprise Server 2016

CVE-2026-20959

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an authorized attacker to perform spoofing over a network.

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.070 (93.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.6 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N.

Affected products

Microsoft Sharepoint Enterprise Server 2016 — versions 16.0.0
Microsoft Sharepoint Server 2019 — versions 16.0.0
Microsoft Sharepoint Server Subscription Edition — versions 16.0.0
Microsoft Sharepoint_server — versions 2016, 2019

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

secure@microsoft.com (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-20959?: CVE-2026-20959 is a medium-severity vulnerability in Microsoft Sharepoint Enterprise Server 2016, classified under Cross-site Scripting. CVSS score: 4.6/10. Published 2026-01-13.
How severe is CVE-2026-20959?: Medium severity. CVSS v3 base score is 4.6 out of 10.