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CVE-2026-102859: Microsoft Office SharePoint Spoofing Vulnerability

• Severity: medium (CVSS 4.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-13 · updated 2026-10-31
• Weakness: CWE-79

Description

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.

Affected products

• Microsoft SharePoint Server: before 16.0.20326.20190 — fixed in 16.0.20326.20190
• Microsoft SharePoint Server Subscription Edition: from 16.0.0 before 16.0.20326.20190 — fixed in 16.0.20326.20190

How to fix

Upgrade to a fixed version: Microsoft SharePoint Server 16.0.20326.20190; Microsoft SharePoint Server Subscription Edition 16.0.20326.20190. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-102859

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