CVE-2025-60726 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 allows an unauthorized attacker to read memory beyond the intended buffer boundaries, leading to local information disclosure. The flaw does not require any privileges (PR:N) but does require user interaction (UI:R), such as opening a malicious Excel file or triggering a specific action within the Office Online Server environment. The vulnerability impacts confidentiality (C:H) and availability (A:H) but does not affect integrity (I:N). The attack vector is local (AV:L), meaning the attacker must have local access to the system, which limits remote exploitation but still poses a significant risk in environments where multiple users share access or where attackers have gained limited footholds. The vulnerability is rated with a CVSS 3.1 score of 7.1, reflecting its high severity. No public exploits or patches are currently available, but the vulnerability is officially published and reserved by Microsoft. The out-of-bounds read could allow attackers to leak sensitive information from memory, potentially exposing credentials, cryptographic keys, or other confidential data processed by Excel Online Server. This could further facilitate privilege escalation or lateral movement within a compromised network. The vulnerability's presence in a widely deployed enterprise collaboration tool increases its potential impact, especially in cloud and hybrid environments where Office Online Server is used to provide Excel functionality through browsers or integrated applications.

For European organizations, this vulnerability poses a significant risk to confidentiality and availability of sensitive data processed via Microsoft Office Online Server. Many enterprises and public sector organizations in Europe rely on Office Online Server for collaborative document editing, making them potential targets. The local attack vector means that insider threats or attackers who have gained limited local access could exploit this flaw to extract sensitive information, potentially including business secrets, personal data protected under GDPR, or credentials that could be used for further attacks. The availability impact could disrupt business operations relying on Excel Online services. Given the high adoption of Microsoft products in Europe, especially in countries with strong digital economies and regulatory environments like Germany, France, and the UK, the risk is amplified. Additionally, sectors such as finance, healthcare, and government, which handle highly sensitive data, could face severe consequences if this vulnerability is exploited. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as attackers often develop exploits rapidly after vulnerability disclosure.

Organizations should prioritize deploying official patches from Microsoft once they become available for Office Online Server version 16.0.0.0. Until patches are released, practical mitigations include restricting local access to Office Online Server hosts to trusted personnel only, implementing strict access controls and monitoring for unusual local user activity. Employ application whitelisting and endpoint detection and response (EDR) tools to detect attempts to exploit memory corruption vulnerabilities. Disable or limit Excel Online Server functionality where feasible, especially in environments with untrusted users. Conduct regular security awareness training to reduce the risk of malicious user interaction required to trigger the vulnerability. Network segmentation can help contain potential exploitation impacts. Additionally, review and harden configurations related to Office Online Server to minimize attack surface, including disabling unnecessary features and services. Maintain up-to-date backups and incident response plans to quickly recover from any exploitation attempts.