What is the CVSS score of CVE-2026-20959?

CVE-2026-20959 has a CVSS 3.1 base score of 4.6 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N. EPSS exploitation probability: 0.1%.

Which versions of Sharepoint Server are affected by CVE-2026-20959?

CVE-2026-20959 presents moderate security risk, a cross-site scripting vulnerability rated CVSS 4.6. Attackers could inject scripts to steal sessions or perform actions as authenticated users.. A patch is available.

How to fix or mitigate CVE-2026-20959?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

Sharepoint Server CVE-2026-20959

MEDIUM

Cross-site Scripting (XSS) (CWE-79)

2026-01-13 secure@microsoft.com

Microsoft XSS Sharepoint Server

4.6

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

4.6 MEDIUM

AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

ENISA EUVD

HIGH

qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

CVE Published

Jan 13, 2026 - 18:16 nvd

MEDIUM 4.6

DescriptionCVE.org

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.

AnalysisAI

Stored XSS in Microsoft SharePoint Server enables authenticated users to inject malicious scripts that execute in other users' browsers, potentially leading to credential theft or session hijacking. The vulnerability requires user interaction and network access, but no patch is currently available, leaving organizations dependent on compensating controls or vendor updates.

Technical ContextAI

Classified as CWE-79 (Cross-site Scripting (XSS)). Affects Sharepoint Server. 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.

RemediationAI

Monitor vendor advisories for a patch. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.