CVE-2025-30378 is a high-severity 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 or sanitization, allowing attackers to manipulate the serialized data to execute arbitrary code. In this case, the vulnerability enables an unauthorized attacker to execute code locally on the affected SharePoint server. The CVSS 3.1 base score of 7.0 reflects a high severity, with an attack vector of local (AV:L), high attack complexity (AC:H), no privileges required (PR:N), and requiring user interaction (UI:R). The impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H), meaning successful exploitation could lead to full system compromise, data theft, or service disruption. The vulnerability does not currently have known exploits in the wild, but the potential for local code execution makes it a significant risk, especially in environments where SharePoint is widely used for collaboration and document management. The lack of available patches at the time of publication increases the urgency for mitigation and monitoring. Given the nature of SharePoint as a critical enterprise collaboration platform, exploitation could lead to unauthorized access to sensitive corporate data and disruption of business processes.

For European organizations, the impact of CVE-2025-30378 could be substantial. SharePoint Enterprise Server 2016 is commonly deployed in medium to large enterprises across Europe for document management, intranet portals, and collaboration. Successful exploitation could allow attackers to execute arbitrary code locally on SharePoint servers, potentially leading to data breaches involving confidential corporate information, intellectual property, and personal data protected under GDPR. The high impact on confidentiality, integrity, and availability could result in operational downtime, loss of trust, regulatory penalties, and financial damage. Additionally, since the vulnerability requires local access and user interaction, insider threats or phishing campaigns targeting employees with access to SharePoint servers could be leveraged to exploit this flaw. The absence of known exploits in the wild currently provides a window for organizations to proactively address the vulnerability before active exploitation occurs.

European organizations should implement the following specific mitigation strategies: 1) Restrict local access to SharePoint Enterprise Server 2016 systems strictly to trusted administrators and users to reduce the attack surface. 2) Enforce strict user access controls and monitor user activity to detect suspicious behavior that could indicate attempts to exploit deserialization flaws. 3) Apply application whitelisting and endpoint protection solutions capable of detecting anomalous code execution patterns on SharePoint servers. 4) Conduct phishing awareness training to minimize the risk of social engineering attacks that could facilitate user interaction required for exploitation. 5) Regularly audit and harden SharePoint configurations, disabling unnecessary features or services that could be leveraged in an attack. 6) Monitor security advisories from Microsoft closely and prepare to apply patches or workarounds as soon as they become available. 7) Implement network segmentation to isolate SharePoint servers from less trusted network zones, limiting lateral movement opportunities. 8) Employ logging and intrusion detection systems focused on SharePoint server activities to enable early detection of exploitation attempts.