CVE-2025-62563 is a use-after-free vulnerability classified under CWE-416 found in Microsoft Office Online Server, specifically impacting Microsoft Office Excel functionality. The vulnerability arises when the software improperly manages memory, freeing an object while it is still in use, which can lead to arbitrary code execution. An attacker can exploit this flaw by convincing a user to open or interact with a specially crafted Excel file hosted or processed via Office Online Server. The vulnerability requires local access (AV:L), low attack complexity (AC:L), no privileges (PR:N), but does require user interaction (UI:R). The scope is unchanged (S:U), and the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H). This means successful exploitation could lead to full system compromise on the affected host. The vulnerability was reserved on 2025-10-15 and published on 2025-12-09, with no known exploits in the wild and no patches currently available. The affected version is 16.0.0.0 of Office Online Server, a widely used enterprise product for hosting Office applications online. The lack of patches and the high impact score necessitate urgent attention from organizations using this product. The vulnerability's exploitation vector being local and requiring user interaction limits remote exploitation but still poses a significant risk in environments where users access Office Online Server-hosted Excel files.

For European organizations, this vulnerability poses a significant risk due to the widespread use of Microsoft Office Online Server in enterprise environments, including government, finance, healthcare, and critical infrastructure sectors. Successful exploitation could lead to unauthorized code execution on servers or user machines, potentially resulting in data breaches, disruption of services, or lateral movement within networks. The high impact on confidentiality, integrity, and availability means sensitive data could be exposed or altered, and system availability could be compromised. Given the local access requirement, insider threats or compromised user endpoints could be leveraged to exploit this vulnerability. The absence of patches increases the window of exposure, making proactive mitigation critical. Organizations relying heavily on Office Online Server for collaborative document editing and sharing are particularly vulnerable, as attackers could craft malicious Excel files to target users. This could disrupt business operations and damage trust in digital collaboration tools.

1. Limit local access to systems running Microsoft Office Online Server to trusted personnel only and enforce strict access controls. 2. Educate users about the risks of opening untrusted or unexpected Excel files, especially those accessed via Office Online Server. 3. Monitor logs and network traffic for unusual activity related to Office Online Server and Excel file processing. 4. Implement application whitelisting and endpoint protection solutions capable of detecting anomalous behavior indicative of exploitation attempts. 5. Prepare for rapid deployment of official patches or updates from Microsoft once they become available. 6. Consider isolating Office Online Server environments from critical network segments to contain potential compromises. 7. Regularly back up critical data and verify restoration procedures to minimize impact from potential exploitation. 8. Employ multi-factor authentication and robust identity management to reduce the risk of unauthorized local access. 9. Review and harden configuration settings of Office Online Server to minimize attack surface. 10. Engage with Microsoft support channels for any available workarounds or advisories related to this vulnerability.