CVE-2025-29820 is a high-severity use-after-free vulnerability (CWE-416) affecting Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. The vulnerability arises from improper memory management in Microsoft Office Word components integrated or used within SharePoint environments. A use-after-free flaw occurs when a program continues to use a pointer after the memory it points to has been freed, leading to undefined behavior. In this case, the flaw allows an unauthorized attacker to execute arbitrary code locally on the affected system. The attack vector requires local access (AV:L), no privileges (PR:N), but does require user interaction (UI:R), such as opening a malicious document or triggering a crafted action within SharePoint that invokes the vulnerable Word component. The vulnerability impacts confidentiality, integrity, and availability, as successful exploitation can lead to full code execution with high impact on all three security properties. The CVSS 3.1 base score is 7.8, reflecting a high severity level. No known exploits are currently reported in the wild, and no official patches have been linked yet. The vulnerability was reserved in March 2025 and published in April 2025, indicating recent discovery and disclosure. The flaw is particularly concerning in enterprise environments where SharePoint is widely used for document management and collaboration, as it could be leveraged to compromise internal systems if an attacker convinces a user to interact with malicious content. The vulnerability scope is local, but the potential for lateral movement or privilege escalation exists if exploited successfully within a corporate network.

For European organizations, this vulnerability poses a significant risk due to the widespread adoption of Microsoft SharePoint Enterprise Server 2016 in corporate, governmental, and educational institutions. Exploitation could lead to unauthorized code execution on critical servers or user workstations, potentially resulting in data breaches, disruption of document management workflows, and compromise of sensitive information. Given the high confidentiality, integrity, and availability impacts, attackers could deploy malware, ransomware, or conduct espionage activities. The requirement for user interaction limits remote exploitation but does not eliminate risk, especially in environments where users frequently handle documents via SharePoint portals. The lack of known exploits currently reduces immediate threat but organizations should prepare for potential future attacks. The vulnerability could also be leveraged in targeted attacks against European entities, especially those with high-value intellectual property or sensitive data stored in SharePoint.

European organizations should implement a multi-layered mitigation strategy: 1) Monitor Microsoft’s official channels for patches addressing CVE-2025-29820 and apply them promptly once available. 2) Restrict local user permissions to minimize the impact of local code execution vulnerabilities. 3) Educate users on the risks of opening untrusted documents or interacting with suspicious SharePoint content to reduce the likelihood of user interaction exploitation. 4) Employ application whitelisting and endpoint protection solutions capable of detecting anomalous behavior related to memory corruption exploits. 5) Use network segmentation to isolate SharePoint servers and limit lateral movement in case of compromise. 6) Conduct regular vulnerability assessments and penetration testing focused on SharePoint environments to identify and remediate weaknesses proactively. 7) Implement strict document upload and validation policies on SharePoint portals to prevent malicious content from being introduced. 8) Enable logging and monitoring on SharePoint servers to detect suspicious activities indicative of exploitation attempts.