CVE-2025-24082 is a high-severity use-after-free vulnerability (CWE-416) identified in Microsoft Office Online Server, specifically affecting version 1.0.0. The vulnerability arises from improper memory management in the handling of Microsoft Office Excel files within the Office Online Server environment. A use-after-free condition occurs when the software continues to use a pointer to memory after it has been freed, leading to undefined behavior. In this case, an unauthorized attacker can exploit this flaw to execute arbitrary code locally on the server hosting Office Online Server. The CVSS 3.1 base score is 7.8, reflecting a high impact on confidentiality, integrity, and availability. The attack vector is local (AV:L), meaning the attacker must have local access to the system, but no privileges are required (PR:N). User interaction is required (UI:R), implying that the attacker must trick a user into triggering the vulnerability, for example, by opening a specially crafted Excel document through the Office Online Server interface. The vulnerability affects the initial release version 1.0.0 of Office Online Server, which is used to provide browser-based access to Microsoft Office applications. Although no known exploits are currently reported in the wild, the vulnerability is publicly disclosed and considered critical enough to warrant immediate attention. The lack of available patches at the time of disclosure increases the urgency for organizations to implement mitigations and monitor for updates from Microsoft. This vulnerability could allow attackers to gain code execution capabilities on the server, potentially leading to full system compromise, data theft, or disruption of services.

For European organizations, the impact of CVE-2025-24082 could be significant, especially for those relying on Microsoft Office Online Server to provide collaborative document editing and viewing capabilities within their intranet or cloud environments. Successful exploitation could lead to unauthorized code execution on critical servers, resulting in potential data breaches, service outages, or lateral movement within corporate networks. This is particularly concerning for sectors with stringent data protection requirements such as finance, healthcare, and government institutions across Europe. The compromise of Office Online Server could expose sensitive documents and intellectual property, undermining confidentiality and integrity. Additionally, disruption of Office Online Server services could impact business continuity and productivity. Given the local attack vector and requirement for user interaction, insider threats or targeted phishing campaigns could be leveraged to exploit this vulnerability. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, as attackers may develop exploits following public disclosure.

European organizations should take proactive steps to mitigate the risk posed by CVE-2025-24082. First, they should monitor Microsoft’s official channels for patches or security updates addressing this vulnerability and apply them promptly once available. Until patches are released, organizations should restrict local access to servers running Office Online Server to trusted administrators only, minimizing the attack surface. Implementing strict access controls and monitoring for unusual activity on these servers is critical. Additionally, organizations should educate users about the risks of opening untrusted Excel documents via Office Online Server and implement email filtering and attachment scanning to reduce the likelihood of malicious files reaching users. Employing application whitelisting and endpoint detection and response (EDR) solutions on servers can help detect and prevent exploitation attempts. Network segmentation to isolate Office Online Server from sensitive systems can limit potential lateral movement. Finally, conducting regular security assessments and penetration testing focused on Office Online Server deployments can help identify and remediate configuration weaknesses.