CVE-2025-53770 is a critical remote code execution vulnerability in Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. The vulnerability arises from the deserialization of untrusted data (CWE-502), a common and dangerous security flaw where an attacker can manipulate serialized objects to execute arbitrary code upon deserialization. In this case, the flaw allows an unauthenticated attacker to send crafted data over the network to a vulnerable SharePoint server, triggering the deserialization process and enabling remote code execution without requiring user interaction or prior authentication. The CVSS v3.1 base score of 9.8 reflects the high severity, with attack vector being network-based, no privileges or user interaction required, and full impact on confidentiality, integrity, and availability. Microsoft has acknowledged the existence of exploits in the wild and is preparing a comprehensive patch, but as of the published date, no official patch has been released. Organizations are advised to implement interim mitigations as recommended by Microsoft to reduce exposure. Given SharePoint's role as a widely used enterprise collaboration and document management platform, successful exploitation could lead to complete system compromise, data theft, lateral movement within corporate networks, and disruption of business operations.

For European organizations, the impact of CVE-2025-53770 is significant due to the widespread adoption of Microsoft SharePoint Enterprise Server 2016 in government, financial, healthcare, and large enterprise sectors across Europe. Exploitation could lead to unauthorized access to sensitive corporate and personal data protected under GDPR, resulting in regulatory penalties and reputational damage. The ability to execute arbitrary code remotely without authentication increases the risk of ransomware deployment, espionage, and sabotage. Disruption of SharePoint services could impact critical business processes and collaboration workflows. Furthermore, given the interconnected nature of European supply chains and public sector networks, a successful attack could propagate beyond the initial victim, amplifying the overall risk. The vulnerability's network-based attack vector and lack of required user interaction make it particularly dangerous in environments with internet-facing SharePoint servers or insufficient network segmentation.

1. Immediately apply any interim mitigations recommended by Microsoft in the official CVE documentation, such as disabling vulnerable deserialization features or restricting access to SharePoint services via network-level controls (firewalls, VPNs). 2. Restrict inbound network traffic to SharePoint servers to trusted IP addresses and internal networks only, minimizing exposure to the internet. 3. Implement strict network segmentation and monitoring to detect anomalous deserialization activity or unusual remote code execution attempts. 4. Employ application-layer firewalls or Web Application Firewalls (WAFs) with updated signatures to detect and block exploit attempts targeting this vulnerability. 5. Prepare for rapid deployment of the official security update once released by Microsoft, including testing in controlled environments to ensure compatibility. 6. Conduct thorough audits of SharePoint server configurations and logs to identify any signs of compromise or attempted exploitation. 7. Educate IT and security teams about the vulnerability specifics and ensure incident response plans are updated to handle potential exploitation scenarios. 8. Consider deploying endpoint detection and response (EDR) solutions on SharePoint servers to detect malicious behaviors indicative of exploitation.