CVE-2025-24081 is a use-after-free vulnerability classified under CWE-416, found in Microsoft Office Online Server version 1.0.0, specifically within the Excel component. Use-after-free vulnerabilities occur when a program continues to use a pointer after the memory it points to has been freed, leading to undefined behavior including potential arbitrary code execution. In this case, an unauthorized attacker with local access can exploit this flaw to execute code on the affected system. The vulnerability does not require privileges (PR:N) but does require user interaction (UI:R), such as opening or interacting with a malicious Excel document hosted or processed by the Office Online Server. The CVSS 3.1 vector indicates low attack complexity (AC:L) and local attack vector (AV:L), with high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no public exploits are known yet, the vulnerability is critical due to the potential for local code execution and system compromise. Office Online Server is used by enterprises to provide web-based access to Office documents, making this vulnerability a risk for environments where users access Excel files online. The lack of available patches at the time of publication increases the urgency for mitigation through access control and monitoring.

For European organizations, this vulnerability poses a significant risk to the confidentiality, integrity, and availability of data processed via Microsoft Office Online Server. Since the vulnerability allows local code execution, attackers could potentially escalate privileges, deploy malware, or disrupt business operations by corrupting or deleting critical Excel documents. Organizations relying on Office Online Server for collaborative workflows, especially in finance, government, and critical infrastructure sectors, could face data breaches or operational downtime. The requirement for local access limits remote exploitation but insider threats or compromised endpoints could be leveraged to exploit this vulnerability. The high impact on all security triad components means that sensitive European data, including personal data protected under GDPR, could be exposed or manipulated. This could lead to regulatory penalties and reputational damage. Additionally, the collaborative nature of Office Online Server means that a single compromised user could affect multiple users or systems within an organization.

1. Apply official patches from Microsoft as soon as they become available to address CVE-2025-24081. 2. Until patches are released, restrict local access to Office Online Server systems to trusted personnel only and enforce strict user privilege separation. 3. Implement application whitelisting and endpoint protection solutions to detect and prevent exploitation attempts involving Office Online Server processes. 4. Monitor logs and system behavior for unusual activity related to Excel file processing or Office Online Server services, including unexpected process launches or memory anomalies. 5. Educate users about the risks of interacting with untrusted Excel documents, especially in environments where Office Online Server is accessible. 6. Consider network segmentation to isolate Office Online Server from less trusted network zones to reduce the risk of lateral movement. 7. Employ multi-factor authentication and strong access controls for administrative interfaces of Office Online Server to prevent unauthorized configuration changes. 8. Regularly audit and update software inventories to ensure all Office Online Server instances are identified and managed appropriately.