ASP.NET

Cybercriminals Exploit Critical SharePoint Vulnerability CVE-2025-53770 for Remote Code Execution

A critical unauthenticated remote code execution flaw in Microsoft SharePoint Server, tracked as CVE-2025-53770 with a CVSS score of 9.8, is being actively exploited in the wild. The vulnerability stems from unsafe deserialization of data sent to on-premises servers and forms part of the ToolShell attack chain alongside CVE-2025-49704 and CVE-2025-49706. Attackers can execute arbitrary commands, install web shells, and steal ASP.NET cryptographic keys to forge authentication tokens and maintain persistence even after patching. The flaw affects SharePoint Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition, while SharePoint Online in Microsoft 365 remains unaffected. Two related variants, CVE-2025-53770 and CVE-2025-53771, were developed to bypass earlier mitigations. Administrators are urged to apply all available patches immediately, restrict internet exposure of SharePoint, and hunt for suspicious files, processes, and scheduled tasks.