CVE-2025-54897 is a vulnerability classified under CWE-502 (Deserialization of Untrusted Data) affecting Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. The flaw arises when SharePoint improperly handles deserialization of data from untrusted sources, allowing an attacker with authorized access and low privileges to craft malicious serialized objects. When these objects are deserialized by the server, arbitrary code execution can occur remotely over the network without requiring user interaction. The vulnerability has a CVSS 3.1 base score of 8.8, indicating high severity, with attack vector being network (AV:N), low attack complexity (AC:L), privileges required (PR:L), no user interaction (UI:N), and full impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no known exploits are currently in the wild, the vulnerability poses a significant risk due to the widespread use of SharePoint in enterprise environments for document management and collaboration. The flaw could allow attackers to compromise SharePoint servers, potentially leading to data breaches, lateral movement within networks, and disruption of business operations. The lack of an available patch at the time of publication increases the urgency for mitigation through alternative controls.

For European organizations, this vulnerability threatens the confidentiality, integrity, and availability of critical business data managed via SharePoint 2016. Exploitation could lead to unauthorized data access, modification, or deletion, severely impacting business continuity and regulatory compliance, especially under GDPR. The ability to execute code remotely without user interaction increases the risk of rapid compromise and lateral movement within corporate networks. Sectors such as finance, government, healthcare, and manufacturing that rely heavily on SharePoint for collaboration and document management are particularly vulnerable. Disruption or data breaches could result in significant financial losses, reputational damage, and legal consequences. The vulnerability's network-based attack vector means that organizations with exposed SharePoint servers or insufficient network segmentation are at higher risk. Given the high adoption rate of Microsoft products across Europe, the potential impact is broad and severe.

1. Apply official Microsoft patches immediately once they become available to remediate the vulnerability. 2. Until patches are released, 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 for SharePoint users to reduce the risk posed by low-privilege attackers. 4. Monitor SharePoint logs and network traffic for unusual deserialization activity or anomalous behavior indicative of exploitation attempts. 5. Employ application-layer security controls such as Web Application Firewalls (WAFs) configured to detect and block malicious serialized payloads. 6. Conduct regular security assessments and penetration tests focusing on deserialization vulnerabilities and SharePoint configurations. 7. Educate IT and security teams about the risks of deserialization vulnerabilities and the importance of timely patching and monitoring. 8. Consider isolating SharePoint environments or using virtual patching techniques if immediate patching is not feasible.