CVE-2025-47166 is a high-severity vulnerability classified under CWE-502, which pertains to the deserialization of untrusted data. This vulnerability affects Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. Deserialization vulnerabilities occur when an application deserializes data from untrusted sources without sufficient validation, allowing attackers to manipulate the serialized data to execute arbitrary code. In this case, an authorized attacker with legitimate access privileges to the SharePoint environment can exploit this vulnerability remotely over the network to execute arbitrary code. The vulnerability does not require user interaction and has a low attack complexity, making exploitation feasible in environments where an attacker has at least some level of authorized access. The CVSS v3.1 base score is 8.8, indicating a high level of severity with significant impact on confidentiality, integrity, and availability. The vulnerability allows complete compromise of the affected SharePoint server, potentially enabling attackers to execute malicious payloads, escalate privileges, move laterally within the network, and exfiltrate sensitive data. No known exploits are currently reported in the wild, and no patches or mitigations have been officially released as of the publication date (June 10, 2025). Given the critical role SharePoint often plays in enterprise collaboration and document management, exploitation could severely disrupt business operations and lead to data breaches.

For European organizations, the impact of CVE-2025-47166 could be substantial. SharePoint Enterprise Server 2016 is widely used across various sectors including government, finance, healthcare, and manufacturing in Europe for document management and collaboration. Exploitation could lead to unauthorized code execution on critical servers, resulting in data theft, alteration, or destruction. This could compromise sensitive personal data protected under GDPR, leading to regulatory penalties and reputational damage. Additionally, disruption of SharePoint services could halt business workflows, affecting productivity and service delivery. The vulnerability’s network-based exploitation and lack of user interaction requirement increase the risk of rapid spread within corporate networks. European organizations with complex IT environments and legacy SharePoint deployments are particularly at risk, especially if they have not applied recent security updates or do not have robust network segmentation and monitoring in place.

Given the absence of an official patch at the time of disclosure, European organizations should implement several specific mitigations: 1) Restrict SharePoint administrative and user access strictly to trusted personnel and enforce the principle of least privilege to limit the potential attacker base. 2) Employ network segmentation and firewall rules to isolate SharePoint servers from less trusted network zones and limit inbound access to only necessary management and user endpoints. 3) Monitor SharePoint server logs and network traffic for unusual deserialization activity or anomalous remote code execution attempts using advanced threat detection tools. 4) Consider deploying application-layer firewalls or Web Application Firewalls (WAFs) with custom rules to detect and block suspicious serialized payloads targeting SharePoint. 5) Prepare for rapid patch deployment by establishing a vulnerability management process that includes testing and applying updates as soon as Microsoft releases an official fix. 6) Conduct internal security awareness training to ensure that authorized users understand the risks of privilege misuse and report suspicious activity promptly. 7) Evaluate the feasibility of upgrading to a more recent SharePoint version with improved security features if long-term support for 2016 is ending.