What is CVE-2026-55021?

CVE-2026-55021 is a high-severity vulnerability in Microsoft Sharepoint Enterprise Server 2016, classified under Cross-site Scripting. CVSS score: 7.3/10. Published 2026-07-14.

How severe is CVE-2026-55021?

High severity. CVSS v3 base score is 7.3 out of 10.

XSS in Microsoft Sharepoint Enterprise Server 2016

CVE-2026-55021

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)

CVSS v3 metric

CVSS v3 base score 7.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/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

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

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

Frequently asked questions

What is CVE-2026-55021?: CVE-2026-55021 is a high-severity vulnerability in Microsoft Sharepoint Enterprise Server 2016, classified under Cross-site Scripting. CVSS score: 7.3/10. Published 2026-07-14.
How severe is CVE-2026-55021?: High severity. CVSS v3 base score is 7.3 out of 10.