Critical Microsoft SharePoint Vulnerability Allows Remote Code Execution via SafeControls Bypass
A vulnerability tracked as CVE-2026-65660 with a CVSS score of 8.8 affects Microsoft SharePoint Server 2016, SharePoint Server 2019, and Subscription Edition. The flaw permits an authenticated low-privileged attacker to achieve arbitrary code execution on on-premises servers. It stems from improper handling of quotes in attacker-controlled Register directives within the ToolPane component, bypassing the SafeControls mechanism. This allows registration of dangerous .NET classes followed by deserialization-based remote code execution. Microsoft released patches on August 11, 2026, and initially reported no public disclosure or exploitation. Publication of a detailed technical analysis has now increased the risk for unpatched installations.
BoletimSecSep 23, 2026Translated from Portuguese