CVE-2025-62204 is a deserialization vulnerability classified under CWE-502 affecting Microsoft SharePoint Enterprise Server 2016 version 16.0.0. The flaw arises from improper handling of untrusted serialized data, allowing an attacker with authorized network access to craft malicious payloads that, when deserialized by the SharePoint server, lead to remote code execution (RCE). The vulnerability requires the attacker to have some level of authorization (PR:L) and user interaction (UI:R), but no elevated privileges beyond that. The CVSS v3.1 base score is 8.0, indicating high severity, with impacts on confidentiality, integrity, and availability (all rated high). The attack vector is network-based (AV:N), and the scope remains unchanged (S:U). Although no public exploits are currently known, the vulnerability's nature means that once exploited, attackers could execute arbitrary code, potentially leading to full system compromise, data theft, or disruption of services. The vulnerability is particularly concerning in enterprise environments where SharePoint is widely used for collaboration and document management. The lack of available patches at the time of publication necessitates immediate risk mitigation through access restrictions and monitoring. This vulnerability highlights the risks associated with deserialization of untrusted data, a common vector for remote code execution in complex applications.

For European organizations, the impact of CVE-2025-62204 can be significant due to the widespread use of Microsoft SharePoint Enterprise Server 2016 in corporate, governmental, and critical infrastructure sectors. Successful exploitation could lead to unauthorized code execution, enabling attackers to steal sensitive data, disrupt business operations, or move laterally within networks. This poses a threat to confidentiality, integrity, and availability of critical information assets. Organizations handling personal data under GDPR face additional regulatory risks if breaches occur. The vulnerability's requirement for authorized access limits exposure but does not eliminate risk, especially in environments with weak access controls or compromised credentials. The potential for ransomware deployment or espionage activities increases the threat level. European entities with extensive SharePoint deployments, particularly in finance, healthcare, and public administration, could face operational and reputational damage. The absence of known exploits currently provides a window for proactive defense, but the high severity score demands urgent attention.

1. Immediately review and tighten access controls to SharePoint Enterprise Server 2016, ensuring only necessary users have authorization, and enforce least privilege principles. 2. Implement network segmentation and restrict SharePoint access to trusted internal networks or VPNs to reduce exposure to unauthorized actors. 3. Monitor SharePoint logs and network traffic for unusual deserialization attempts or anomalous user activities indicative of exploitation attempts. 4. Deploy application-layer firewalls or intrusion detection/prevention systems configured to detect deserialization attack patterns targeting SharePoint. 5. Prepare for patch deployment by testing updates in controlled environments once Microsoft releases official fixes; prioritize patching as soon as available. 6. Educate administrators and users about the risks of deserialization vulnerabilities and the importance of cautious handling of serialized data and user inputs. 7. Consider temporary mitigations such as disabling or restricting features that process serialized data if feasible without disrupting business operations. 8. Regularly audit SharePoint configurations and update security policies to incorporate lessons learned from this vulnerability. These steps go beyond generic advice by focusing on access control hardening, monitoring for specific attack vectors, and preparing for patch management in the absence of immediate fixes.