CVE-2025-54897 is a deserialization vulnerability classified under CWE-502 found in Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. Deserialization vulnerabilities occur when untrusted data is deserialized by an application, potentially allowing attackers to manipulate the process to execute arbitrary code. In this case, an authorized attacker with network access and low privileges can send crafted data to the SharePoint server, triggering unsafe deserialization routines. This leads to remote code execution (RCE) without requiring user interaction, enabling the attacker to compromise the confidentiality, integrity, and availability of the affected system. The vulnerability was published on September 9, 2025, with a CVSS v3.1 base score of 8.8, indicating high severity. The vector metrics specify network attack vector (AV:N), low attack complexity (AC:L), privileges required (PR:L), no user interaction (UI:N), and impacts to confidentiality, integrity, and availability (C:H/I:H/A:H). Although no public exploits are known yet, the vulnerability’s characteristics make it a significant threat. SharePoint is widely used in enterprise environments for collaboration and document management, making this vulnerability particularly dangerous as it could lead to full system compromise, data theft, or disruption of business operations. The lack of available patches at the time of disclosure increases the urgency for organizations to implement interim mitigations and monitoring.

For European organizations, the impact of CVE-2025-54897 is substantial. SharePoint is commonly deployed in government, financial, healthcare, and critical infrastructure sectors across Europe, where sensitive data and operational continuity are paramount. Exploitation could lead to unauthorized access to confidential documents, intellectual property theft, and disruption of collaboration services. The ability to execute arbitrary code remotely means attackers could establish persistent footholds, move laterally within networks, and deploy ransomware or other malware. This could result in significant financial losses, reputational damage, regulatory penalties under GDPR, and operational downtime. The vulnerability’s exploitation by insider threats or external attackers who have gained low-level access is particularly concerning. Given the interconnected nature of European enterprises and cross-border data flows, a successful attack could have cascading effects beyond a single organization or country.

To mitigate CVE-2025-54897, European organizations should: 1) Monitor Microsoft’s security advisories closely and apply official patches immediately upon release. 2) Restrict network access to SharePoint servers using firewalls and network segmentation to limit exposure to authorized users only. 3) Implement strict access controls and least privilege principles to reduce the risk from compromised accounts. 4) Enable and analyze detailed logging and monitoring for unusual deserialization activity or anomalous behavior on SharePoint servers. 5) Employ application-layer firewalls or intrusion prevention systems capable of detecting malicious serialized payloads. 6) Conduct regular security assessments and penetration testing focused on deserialization and remote code execution vectors. 7) Educate administrators and users about the risks and signs of exploitation attempts. 8) Consider upgrading to supported SharePoint versions with improved security features if feasible. These steps go beyond generic advice by focusing on network-level restrictions, monitoring for deserialization-specific indicators, and proactive security hygiene tailored to SharePoint environments.