CVE-2025-54902 is an out-of-bounds read vulnerability classified under CWE-125 found in Microsoft Office Online Server's Excel component, version 16.0.0.0. This vulnerability arises when the software improperly handles memory boundaries, allowing an attacker to read data outside the intended buffer. Such memory corruption can lead to local code execution without requiring any privileges, though user interaction is necessary to trigger the exploit. The vulnerability affects confidentiality, integrity, and availability by potentially allowing arbitrary code execution, which could lead to data leakage, unauthorized modifications, or denial of service. The attack vector is local (AV:L), meaning the attacker must have local access to the system, and the attack complexity is low (AC:L), indicating no special conditions are needed beyond user interaction. The scope is unchanged (S:U), so the impact is limited to the vulnerable component. Currently, there are no known exploits in the wild, but the vulnerability is publicly disclosed and rated with a CVSS 3.1 score of 7.8, indicating high severity. No patches are listed yet, so organizations must monitor for updates. The vulnerability is significant because Office Online Server is widely used in enterprise environments to provide web-based Office functionality, and Excel is a critical application for many business processes. Exploitation could allow attackers to run arbitrary code locally, potentially leading to further compromise if combined with privilege escalation or lateral movement techniques.

For European organizations, this vulnerability poses a substantial risk particularly to enterprises relying on Microsoft Office Online Server for Excel-based workflows. Successful exploitation could lead to unauthorized code execution on servers hosting Office Online Server, potentially exposing sensitive financial, operational, or personal data processed via Excel documents. This could disrupt business continuity, cause data breaches, and lead to regulatory non-compliance under GDPR due to confidentiality breaches. The local attack vector limits remote exploitation, but insider threats or compromised user accounts could be leveraged to trigger the vulnerability. Organizations in finance, government, healthcare, and critical infrastructure sectors are especially vulnerable due to their reliance on Excel and Office Online Server for critical operations. The absence of known exploits currently provides a window for proactive mitigation, but the high severity score indicates that once exploited, the impact could be severe.

1. Monitor Microsoft security advisories closely and apply official patches immediately upon release to remediate the vulnerability. 2. Restrict local access to Office Online Server hosts to trusted personnel only, employing strict access controls and multi-factor authentication. 3. Implement application whitelisting and endpoint protection solutions to detect and block suspicious code execution attempts on servers. 4. Conduct regular security audits and vulnerability scans focusing on Office Online Server deployments. 5. Educate users about the risks of interacting with untrusted Excel files or components within the Office Online environment. 6. Employ network segmentation to isolate Office Online Server infrastructure from less trusted network zones to limit lateral movement. 7. Monitor logs and system behavior for anomalies indicative of exploitation attempts, such as unusual process creation or memory access patterns. 8. Consider disabling or limiting Excel functionality in Office Online Server if feasible until patches are applied.