CVE-2025-53771 is a vulnerability classified under CWE-287 (Improper Authentication) affecting Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. This flaw allows an unauthorized attacker to perform spoofing attacks over a network by bypassing or circumventing the authentication mechanisms implemented in SharePoint. Improper authentication means that the system fails to correctly verify the identity of users or systems attempting to access resources, enabling attackers to impersonate legitimate users or services. The vulnerability has a CVSS 3.1 base score of 6.5, indicating a medium severity level. The vector metrics show that the attack can be performed remotely over the network (AV:N), requires no privileges (PR:N), and no user interaction (UI:N). The impact affects confidentiality and integrity (C:L/I:L) but does not affect availability (A:N). The exploitability is rated as proof-of-concept (E:P), with official remediation (RL:O) and confirmed report confidence (RC:C). No known exploits are currently observed in the wild, and no official patches have been linked yet. Given SharePoint's role as a collaborative platform widely used in enterprises for document management and intranet portals, this vulnerability could allow attackers to spoof identities and potentially gain unauthorized access to sensitive information or manipulate data within the SharePoint environment. This could lead to data leakage, unauthorized data modification, or further lateral movement within an organization's network.

For European organizations, the impact of this vulnerability can be significant due to the widespread adoption of Microsoft SharePoint Enterprise Server 2016 in corporate, governmental, and educational institutions. Unauthorized spoofing could lead to exposure of confidential documents, intellectual property theft, or manipulation of critical business information. This is particularly concerning for sectors with strict data protection regulations such as GDPR, where unauthorized access or data breaches can result in heavy fines and reputational damage. Additionally, the integrity compromise could affect decision-making processes and operational workflows dependent on SharePoint data. Since the vulnerability does not require user interaction or privileges, attackers could automate exploitation attempts remotely, increasing the risk of large-scale attacks. The absence of known exploits in the wild currently provides a window for organizations to prepare and mitigate before active exploitation occurs.

Organizations should prioritize the following specific actions: 1) Conduct an immediate inventory to identify all instances of Microsoft SharePoint Enterprise Server 2016 version 16.0.0 in their environment. 2) Monitor official Microsoft security advisories closely for the release of patches or workarounds addressing CVE-2025-53771 and apply them promptly once available. 3) Implement network-level access controls to restrict SharePoint server access to trusted internal networks or VPNs, minimizing exposure to external attackers. 4) Employ multi-factor authentication (MFA) for SharePoint access where possible to add an additional layer of identity verification beyond the vulnerable authentication mechanism. 5) Use network intrusion detection systems (IDS) and security information and event management (SIEM) tools to detect anomalous authentication attempts or spoofing activities targeting SharePoint servers. 6) Review and tighten SharePoint permissions and audit logs regularly to detect unauthorized access or changes. 7) Consider deploying web application firewalls (WAF) with custom rules to detect and block suspicious authentication traffic patterns. These targeted mitigations go beyond generic advice by focusing on compensating controls and proactive monitoring until an official patch is available.