CVE-2025-49706 is a vulnerability classified under CWE-287 (Improper Authentication) affecting Microsoft SharePoint Enterprise Server 2016, specifically version 16.0.0. The vulnerability allows an attacker without any privileges or user interaction to spoof authentication over a network, potentially impersonating legitimate users or services. This spoofing can lead to unauthorized access to sensitive information or manipulation of data within SharePoint environments. The vulnerability is network exploitable (AV:N), requires low attack complexity (AC:L), and no privileges or user interaction (PR:N/UI:N), making it relatively easy to exploit remotely. The scope is unchanged (S:U), meaning the impact is confined to the vulnerable component. The confidentiality and integrity impacts are low (C:L/I:L), with no impact on availability (A:N). Although no known exploits are currently active in the wild and no patches have been published, the vulnerability poses a credible risk to organizations relying on SharePoint 2016 for collaboration and document management. The flaw arises from improper authentication mechanisms that fail to adequately verify the identity of connecting entities, enabling spoofing attacks that can bypass normal access controls. This could facilitate further attacks, including data exfiltration or privilege escalation if combined with other vulnerabilities.

For European organizations, this vulnerability threatens the confidentiality and integrity of data managed within SharePoint Enterprise Server 2016 environments. SharePoint is widely used across European enterprises, government agencies, and critical infrastructure sectors for document management and collaboration. Exploitation could allow attackers to impersonate legitimate users or services, potentially accessing sensitive documents, altering records, or injecting malicious content. This could lead to data breaches, regulatory non-compliance (e.g., GDPR violations), and erosion of trust in organizational IT systems. While availability is not directly impacted, the indirect consequences of unauthorized access could disrupt business operations and decision-making. The medium severity rating reflects the balance between ease of exploitation and limited impact scope. However, the lack of authentication requirements and network-level exploitability increase the risk profile. European organizations with legacy SharePoint 2016 deployments that have not been upgraded or segmented are particularly vulnerable. The absence of known exploits provides a window for proactive defense but also means attackers could develop exploits rapidly once details are publicized.

1. Implement strict network segmentation and firewall rules to limit access to SharePoint Enterprise Server 2016 instances only to trusted internal networks and authorized endpoints. 2. Monitor network traffic for anomalous authentication attempts or spoofing indicators using intrusion detection/prevention systems (IDS/IPS) and security information and event management (SIEM) tools. 3. Enforce multi-factor authentication (MFA) on all SharePoint access points where possible to add an additional layer of verification beyond the vulnerable authentication mechanism. 4. Regularly audit SharePoint permissions and access logs to detect suspicious activities or unauthorized access patterns. 5. Plan and prioritize upgrading to supported SharePoint versions or applying vendor patches immediately upon release to remediate the vulnerability. 6. Employ endpoint protection and network anomaly detection to identify lateral movement attempts that may follow exploitation. 7. Educate IT and security teams about the vulnerability specifics to improve incident response readiness. 8. Consider deploying web application firewalls (WAFs) with custom rules to detect and block spoofing attempts targeting SharePoint authentication flows.