Summary
Impact: Remote Code Execution. Microsoft rating: Important. Not known to be exploited. Customer action: Required.
Details
How could an attacker exploit the vulnerability?
An authenticated attacker with Site Owner permissions or higher could upload a specially crafted file to the targeted SharePoint Server and craft specialized API requests to trigger deserialization of file's parameters. This would enable the attacker to perform remote code execution in the context of the SharePoint Server.
Security updates
16.0.20326.20136 — https://support.microsoft.com/help/5002908
Vulnerabilities 1
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High 8.8
Microsoft Office SharePoint Remote Code Execution Vulnerability
Deserialization of untrusted data in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
Revision history
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#1
Information published.
References
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CVE-2026-123390 Microsoft Office SharePoint Remote Code Execution Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-123390
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss