Critical Analysis: CVE-2026-45659 - Microsoft SharePoint Server Deserialization of Untrusted Dat... — July 5, 2026

Published 05 Jul 2026 · vulnerability management, CVE analysis, threat intelligence, security operations, cybersecurity news

Initial Discovery and Context Alright, let's talk about CVE-2026-45659. Microsoft just dropped this bomb on July 5th, 2026, and it's a critical remote code execution (RCE) vulnerability stemming from insecure deserialization in SharePoint Server. Specifically, we're looking at SharePoint 2019 and SharePoint Subscription Edition. This one hits hard because SharePoint is often the backbone of an organization's internal collaboration, document management, and sometimes even external-facing portals. It’s an incredibly rich attack surface. When you get RCE on a SharePoint server, you’re usually talking about significant impact – compromise of sensitive data, lateral movement, and persistent access to the internal network. We've seen similar deserialization bugs before, for example, in Exchange, and they consistently lead to some of the nastiest RCE chains. The core issue here is the server pr