CVE-2025-53733 is a vulnerability identified in Microsoft SharePoint Enterprise Server 2016, specifically related to an incorrect conversion between numeric types within Microsoft Office Word components integrated into SharePoint. This vulnerability is classified under CWE-681, which pertains to errors in numeric type conversions that can lead to unexpected behavior or security flaws. The flaw enables an unauthorized attacker to execute arbitrary code locally on the affected system without requiring any privileges or user interaction, as indicated by the CVSS vector (AV:L/AC:L/PR:N/UI:N). This means that an attacker with local access can exploit this vulnerability to gain control over the system, potentially leading to full compromise including confidentiality, integrity, and availability impacts. The vulnerability affects version 16.0.0 of SharePoint Enterprise Server 2016. Although no public exploits have been reported yet, the high CVSS score of 8.4 reflects the severity and potential impact of this issue. The vulnerability arises from improper handling of numeric conversions, which can cause memory corruption or logic errors that attackers can leverage to execute malicious code. Since SharePoint is widely used in enterprise environments for document management and collaboration, exploitation could allow attackers to manipulate sensitive documents or disrupt business operations. The vulnerability was reserved in early July 2025 and published in August 2025, but no patches have been linked yet, indicating that organizations must monitor for updates closely. The lack of required user interaction or privileges increases the risk, especially in environments where local access controls are weak or where attackers can gain local footholds through other means.

For European organizations, the impact of CVE-2025-53733 is significant due to the widespread use of Microsoft SharePoint Enterprise Server 2016 in government, finance, healthcare, and critical infrastructure sectors. Successful exploitation could lead to unauthorized code execution, resulting in data breaches, unauthorized data manipulation, or service disruptions. Confidentiality could be compromised by exposing sensitive documents stored or processed in SharePoint. Integrity risks include unauthorized modification or deletion of critical files, potentially affecting business processes and compliance with regulations such as GDPR. Availability may be impacted if attackers disrupt SharePoint services or leverage the vulnerability to deploy ransomware or other destructive payloads. The local attack vector means that internal threat actors or attackers who have gained limited access to internal networks could escalate their privileges and move laterally. Given the high severity and the critical role of SharePoint in collaboration and document management, the vulnerability poses a substantial risk to operational continuity and data protection obligations within European organizations.

1. Monitor Microsoft security advisories closely and apply official patches or updates as soon as they become available to remediate the vulnerability. 2. Restrict local access to SharePoint servers to trusted administrators only, minimizing the risk of local exploitation. 3. Implement strict access controls and network segmentation to limit the ability of attackers to gain local access to SharePoint systems. 4. Employ application whitelisting and endpoint protection solutions capable of detecting anomalous code execution or memory corruption attempts related to numeric conversion errors. 5. Conduct regular security audits and vulnerability assessments focused on SharePoint environments to identify and remediate potential weaknesses. 6. Educate internal staff about the risks of local access exploitation and enforce least privilege principles. 7. Use monitoring and logging tools to detect unusual activities on SharePoint servers, such as unexpected process executions or privilege escalations. 8. Consider temporary compensating controls such as disabling unnecessary services or features in SharePoint that might be leveraged in exploitation until patches are applied.