CVE-2025-54905 is a high-severity vulnerability classified under CWE-822 (Untrusted Pointer Dereference) affecting Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. The vulnerability arises from an untrusted pointer dereference in Microsoft Office Word components integrated with SharePoint, allowing an unauthorized attacker to disclose sensitive information locally. The flaw occurs when the software dereferences pointers without proper validation, leading to potential access to memory areas that should be restricted. This can result in unauthorized disclosure of confidential data stored or processed by SharePoint. The CVSS 3.1 base score is 7.1, indicating a high severity level. The vector string (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H/E:U/RL:O/RC:C) shows that the attack requires local access (AV:L), low attack complexity (AC:L), no privileges (PR:N), and user interaction (UI:R). The scope is unchanged (S:U), with high impact on confidentiality (C:H), no impact on integrity (I:N), and high impact on availability (A:H). The exploitability is currently unknown in the wild, and no patches have been published yet. The vulnerability could be exploited by tricking a user with local access to open a malicious Word document within SharePoint, leading to information disclosure and potential denial of service due to availability impact. Given the integration of SharePoint with Office Word, this vulnerability could affect workflows relying on document processing and collaboration within enterprise environments.

For European organizations, this vulnerability poses a significant risk, especially for enterprises and public sector entities heavily reliant on Microsoft SharePoint Enterprise Server 2016 for document management and collaboration. The high confidentiality impact means sensitive corporate or governmental data could be exposed if exploited. The availability impact could disrupt critical business processes, causing downtime and productivity loss. Since exploitation requires local access and user interaction, insider threats or compromised endpoints within the network are the most likely attack vectors. Organizations with distributed workforces or hybrid environments where users access SharePoint from various devices may face increased risk. The lack of a patch at the time of disclosure means organizations must rely on mitigations to reduce exposure. The vulnerability could also affect compliance with European data protection regulations such as GDPR if sensitive personal data is disclosed. Overall, the threat could undermine trust in collaboration platforms and lead to financial and reputational damage.

To mitigate this vulnerability, European organizations should implement the following specific measures: 1) Restrict local access to systems running SharePoint Enterprise Server 2016 to trusted users only, enforcing strict access controls and endpoint security policies. 2) Educate users about the risks of opening untrusted Word documents, especially those originating from unknown or suspicious sources, to reduce the likelihood of user interaction exploitation. 3) Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor and block suspicious activities related to Word document processing. 4) Isolate SharePoint servers and limit document upload and processing privileges to minimize exposure to malicious content. 5) Regularly audit and monitor logs for unusual access patterns or errors indicative of exploitation attempts. 6) Prepare for patch deployment by tracking Microsoft updates closely and testing patches in controlled environments before production rollout. 7) Consider deploying network segmentation to separate SharePoint infrastructure from general user networks, reducing lateral movement opportunities. 8) Implement data loss prevention (DLP) controls to detect and prevent unauthorized data exfiltration resulting from exploitation. These targeted actions go beyond generic advice by focusing on controlling local access, user behavior, and monitoring specific to the vulnerability's exploitation requirements.