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CVE-2026-70306: Microsoft Office SharePoint Spoofing Vulnerability

• Severity: critical (CVSS 9.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-11 · updated 2026-10-30
• Weakness: CWE-79

Description

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

Affected products

• Microsoft SharePoint Server: before 16.0.19725.20434; 2016, 2019 — fixed in 16.0.19725.20434
• Microsoft SharePoint Server Subscription Edition: from 16.0.0 before 16.0.19725.20522 — fixed in 16.0.19725.20522
• Microsoft Sharepoint Enterprise Server 2016: from 16.0.0 before 16.0.5565.1001 — fixed in 16.0.5565.1001
• Microsoft SharePoint Server: from 16.0.0 before 16.0.10417.20198 — fixed in 16.0.10417.20198

How to fix

Upgrade to a fixed version: Microsoft SharePoint Server 16.0.19725.20434; Microsoft SharePoint Server Subscription Edition 16.0.19725.20522; Microsoft Sharepoint Enterprise Server 2016 16.0.5565.1001; Microsoft SharePoint Server 16.0.10417.20198. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70306

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