CVE-2025-62202 is an out-of-bounds read vulnerability classified under CWE-125 affecting Microsoft Office Online Server, specifically its Excel processing component in version 16.0.0.0. This vulnerability arises due to improper bounds checking when handling Excel files, allowing an attacker to read memory outside the intended buffer boundaries. Exploitation requires local access to the system and some user interaction but does not require any privileges or authentication. The out-of-bounds read can lead to disclosure of sensitive information residing in adjacent memory areas, compromising confidentiality. Additionally, the vulnerability impacts availability, as the malformed memory access can cause application instability or crashes. The CVSS v3.1 base score is 7.1, reflecting high severity with attack vector local (AV:L), low attack complexity (AC:L), no privileges required (PR:N), and user interaction required (UI:R). The scope is unchanged (S:U), with high confidentiality impact (C:H), no integrity impact (I:N), and high availability impact (A:H). No known exploits have been reported in the wild, and no official patches have been released as of the publication date (November 11, 2025). This vulnerability is significant because Office Online Server is widely used in enterprise environments to provide browser-based Office document editing and collaboration, making it a critical component in many organizations' productivity infrastructure.

For European organizations, this vulnerability poses a significant risk to confidentiality and availability of sensitive data processed through Office Online Server Excel files. Unauthorized local attackers could leverage this flaw to extract sensitive information from memory, potentially exposing intellectual property, personal data, or credentials. The availability impact could disrupt business operations relying on Office Online Server for document collaboration and editing, leading to downtime and productivity loss. Organizations with strict data protection regulations such as GDPR face increased compliance risks if sensitive data is leaked. The requirement for local access limits remote exploitation but insider threats or compromised endpoints could be leveraged to exploit this vulnerability. Given the widespread use of Microsoft Office Online Server in European enterprises, especially in sectors like finance, government, and healthcare, the impact could be substantial if exploited.

1. Restrict local access to systems running Office Online Server to trusted personnel only and enforce strict access controls and monitoring. 2. Implement endpoint security solutions to detect and prevent unauthorized local activities and suspicious user interactions. 3. Monitor system logs and application behavior for anomalies indicative of exploitation attempts or crashes related to Excel processing. 4. Isolate Office Online Server environments from general user workstations to reduce risk of local exploitation. 5. Prepare for rapid deployment of official patches from Microsoft once released; maintain close communication with Microsoft security advisories. 6. Conduct internal audits to identify and secure systems running the affected version (16.0.0.0) and plan for upgrades or mitigations. 7. Educate users about the risks of interacting with untrusted Excel files and enforce policies to limit opening files from unknown sources. 8. Consider implementing application whitelisting and sandboxing techniques to contain potential exploitation.