CVE-2025-54897 is a critical vulnerability identified in Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. The vulnerability is classified under CWE-502, which pertains to the deserialization of untrusted data. Deserialization vulnerabilities occur when an application deserializes data from untrusted sources without sufficient validation or sanitization, potentially allowing attackers to manipulate the serialized data to execute arbitrary code. In this case, an authorized attacker with legitimate access privileges to the SharePoint server can exploit this flaw remotely over the network to execute arbitrary code. The vulnerability does not require user interaction and has a low attack complexity, meaning exploitation is relatively straightforward once access is obtained. The CVSS v3.1 base score of 8.8 reflects the high impact on confidentiality, integrity, and availability, as successful exploitation could lead to full system compromise, data leakage, or disruption of SharePoint services. No known exploits are currently reported in the wild, and no official patches have been linked yet, indicating that organizations should prioritize mitigation and monitoring efforts. The vulnerability affects a widely used enterprise collaboration platform, making it a significant risk for organizations relying on SharePoint 2016 for document management and internal workflows.

For European organizations, the impact of this vulnerability could be severe. SharePoint Enterprise Server 2016 is commonly used across various sectors including government, finance, healthcare, and large enterprises for document management and collaboration. Exploitation could lead to unauthorized access to sensitive corporate or personal data, disruption of critical business processes, and potential compliance violations under regulations such as GDPR. The ability to execute arbitrary code remotely means attackers could deploy ransomware, steal intellectual property, or establish persistent footholds within networks. Given the high confidentiality and integrity impact, organizations could face significant financial losses, reputational damage, and legal consequences. The lack of user interaction requirement increases the risk of automated or targeted attacks. European entities with complex SharePoint deployments or those integrating SharePoint with other critical systems are particularly at risk of cascading effects from this vulnerability.

To mitigate this vulnerability, European organizations should immediately conduct a thorough inventory of SharePoint Enterprise Server 2016 deployments to identify affected systems. Since no official patch is currently available, organizations should implement the following specific measures: 1) Restrict SharePoint administrative and user privileges strictly on a least-privilege basis to minimize the potential attacker base. 2) Employ network segmentation and firewall rules to limit access to SharePoint servers only to trusted internal networks and VPN users. 3) Enable and closely monitor detailed logging and alerting for unusual deserialization or code execution activities within SharePoint environments. 4) Use application-layer firewalls or Web Application Firewalls (WAFs) with custom rules to detect and block suspicious serialized payloads or anomalous requests targeting SharePoint endpoints. 5) Prepare for rapid patch deployment by establishing communication with Microsoft support channels and monitoring for official security updates. 6) Conduct internal penetration testing focused on deserialization attack vectors to identify and remediate potential exploitation paths. 7) Educate administrators and users about the risks of deserialization vulnerabilities and the importance of secure configuration and access controls.