CVE-2026-63520: Microsoft SharePoint Remote Code Execution (FIXED)
Brief
Overview
Rapid7 Labs conducted a zero-day research project against Microsoft SharePoint, resulting in the discovery of two new vulnerabilities that, when chained together, achieve unauthenticated remote code execution (RCE) against a vulnerable SharePoint server. Today, both Rapid7 and Microsoft are disclosing the second vulnerability in this chain, the RCE vulnerability CVE-2026-63520.
The first vulnerability in the chain, CVE-2026-55040, was disclosed by Rapid7 and Microsoft last month.
Our full disclosure timeline for the exploit chain can be seen below in Figure 1.
Figure 1: The road to disclosure.
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CVE-2026-63520 affects all supported versions of Microsoft SharePoint, and certain versions of Microsoft Project Server and Microsoft Office Web Apps Server. For the purpose of our research, we focused solely on SharePoint.