CVE-2025-62561 is a vulnerability classified under CWE-822 (Untrusted Pointer Dereference) affecting Microsoft Office Online Server version 16.0.0.0, specifically within the Microsoft Office Excel component. The flaw arises when the software dereferences pointers that have not been properly validated or sanitized, allowing an attacker to manipulate memory references. This can lead to arbitrary code execution on the local machine without requiring prior authentication, although user interaction is necessary to trigger the exploit. The vulnerability impacts confidentiality, integrity, and availability by enabling unauthorized code execution, potentially allowing attackers to install malware, steal sensitive data, or disrupt services. The CVSS 3.1 base score of 7.8 indicates a high severity, with attack vector being local (AV:L), low attack complexity (AC:L), no privileges required (PR:N), but user interaction required (UI:R). The scope remains unchanged (S:U), and the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). The exploitability is currently theoretical, with no known exploits in the wild, but the vulnerability is publicly disclosed and should be considered a significant risk. The lack of available patches at the time of publication necessitates interim mitigations and heightened monitoring. The vulnerability is particularly relevant for organizations using Office Online Server for collaborative document editing and processing, as exploitation could compromise server integrity and user data.

For European organizations, this vulnerability poses a substantial risk due to widespread use of Microsoft Office Online Server in enterprise environments for document collaboration and processing. Successful exploitation could lead to local code execution on servers, potentially allowing attackers to escalate privileges, move laterally within networks, or disrupt critical business operations. Confidential data processed or stored via Office Online Server could be exposed or manipulated, impacting compliance with GDPR and other data protection regulations. The requirement for local access and user interaction somewhat limits remote exploitation but does not eliminate risk, especially in environments with multiple users or less stringent access controls. Sectors such as finance, healthcare, government, and critical infrastructure, which heavily rely on Microsoft technologies, could face operational disruptions and reputational damage. The absence of known exploits currently provides a window for proactive defense, but the high severity score underscores the urgency for mitigation.

1. Apply security patches promptly once Microsoft releases them for Office Online Server version 16.0.0.0. 2. Until patches are available, restrict local access to Office Online Server systems to trusted personnel only, employing strict access controls and monitoring. 3. Implement application whitelisting and endpoint protection to detect and prevent unauthorized code execution on servers. 4. Educate users about the risks of interacting with untrusted documents or links that could trigger the vulnerability. 5. Monitor system logs and network traffic for unusual activity indicative of exploitation attempts, including unexpected process launches or memory access patterns. 6. Employ network segmentation to isolate Office Online Server infrastructure from critical systems to limit lateral movement in case of compromise. 7. Review and harden user privilege assignments to minimize the impact of local code execution. 8. Conduct regular vulnerability assessments and penetration testing focused on Office Online Server deployments to identify and remediate weaknesses.