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.

BoletimSecTranslated from Portuguese

Read at source

Cybercriminals are actively exploiting a critical vulnerability in Microsoft SharePoint Server that allows remote code execution without authentication or user interaction.

The flaw, registered as CVE-2025-53770, received a CVSS score of 9.8 and impacts on-premises installations of the collaboration platform. It arises from unsafe deserialization of specially crafted data submitted to the server, enabling attackers to run arbitrary commands and fully compromise the system.

The exploitation is part of an attack chain known as ToolShell, which also involves the vulnerabilities CVE-2025-49704 and CVE-2025-49706. The issues CVE-2025-53770 and CVE-2025-53771 emerged as variants specifically designed to circumvent previously applied protections.

Affected products include SharePoint Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition. The cloud-based SharePoint Online service offered through Microsoft 365 is not impacted.

After gaining initial access, threat actors can deploy web shells, run additional tools, and exfiltrate cryptographic keys from ASP.NET. These keys allow attackers to forge valid authentication tokens and retain access even after security updates are installed.

Administrators are advised to deploy all available patches without delay, limit internet exposure of SharePoint servers, and search for suspicious files, processes, and scheduled tasks that may indicate compromise.

Meridian digestThe week's most consequential security stories, distilled into one briefing.See the digest

More in Vulnerabilities & Exploits

CISA Adds Cisco Secure Firewall and GitLab Flaws to Known Exploited Vulnerabilities Catalog
Telegram for Android Patches Voice Call Vulnerability Enabling Code Execution
Yandex Patches Millions of Stations After eMudhra Certificate Keys Compromised