CVE-2025-30378 is a vulnerability classified under CWE-502, which involves the deserialization of untrusted data within Microsoft SharePoint Enterprise Server 2016 (version 16.0.0). Deserialization vulnerabilities occur when an application deserializes data from untrusted sources without sufficient validation, potentially allowing attackers to craft malicious serialized objects that, when deserialized, execute arbitrary code. In this case, an unauthorized attacker can exploit this flaw to execute code locally on the SharePoint server. The CVSS 3.1 base score is 7.0, indicating a high severity level. The attack vector is local (AV:L), meaning the attacker must have local access to the system. The attack complexity is high (AC:H), requiring specific conditions or knowledge to exploit. No privileges are required (PR:N), but user interaction is necessary (UI:R), suggesting that the attacker might need to trick a user into performing an action that triggers the deserialization process. The vulnerability affects confidentiality, integrity, and availability (all rated high impact). Although no public exploits are known at this time, the vulnerability poses a significant risk due to the critical nature of SharePoint in enterprise environments. The lack of an official patch link indicates that remediation may still be pending or in development. Organizations relying on SharePoint 2016 should be aware of this vulnerability and prepare to apply patches promptly once released. Additionally, monitoring and restricting local access to SharePoint servers can reduce exploitation risk.

For European organizations, this vulnerability could lead to unauthorized code execution on SharePoint servers, potentially compromising sensitive corporate data, disrupting collaboration services, and enabling lateral movement within networks. SharePoint is widely used in Europe for document management and collaboration, often containing confidential business and personal data. Exploitation could result in data breaches, loss of data integrity, and service outages, impacting business continuity and regulatory compliance, especially under GDPR. The requirement for local access and user interaction somewhat limits remote exploitation but does not eliminate risk, particularly in environments with shared or poorly secured access. Critical sectors such as finance, government, healthcare, and manufacturing that rely heavily on SharePoint for internal workflows are at heightened risk. The vulnerability could also be leveraged as part of a multi-stage attack to escalate privileges or deploy ransomware. Given the high impact on confidentiality, integrity, and availability, the threat is significant for European enterprises using the affected SharePoint version.

1. Immediately restrict local access to SharePoint Enterprise Server 2016 systems to trusted personnel only, employing strict access controls and network segmentation. 2. Monitor system logs and SharePoint activity for unusual deserialization operations or unexpected user actions that could indicate exploitation attempts. 3. Educate users about the risks of interacting with untrusted content or performing actions that could trigger deserialization vulnerabilities. 4. Implement application whitelisting and endpoint protection solutions capable of detecting and blocking suspicious code execution on SharePoint servers. 5. Prepare to apply official patches or updates from Microsoft as soon as they become available; subscribe to Microsoft security advisories for timely notifications. 6. Consider upgrading to a more recent, supported version of SharePoint that may have improved security controls against deserialization attacks. 7. Conduct regular security assessments and penetration tests focusing on deserialization and related vulnerabilities within SharePoint environments. 8. Employ network-level controls such as host-based firewalls to limit exposure of SharePoint servers to only necessary internal systems. 9. Use multi-factor authentication and strong credential policies to reduce the risk of unauthorized local access. 10. Backup critical SharePoint data regularly and verify restoration procedures to mitigate impact in case of compromise.