CVE-2025-54901 is a buffer over-read vulnerability classified under CWE-126 affecting Microsoft Office Excel 2019, specifically version 19.0.0. This vulnerability allows an unauthorized attacker with local access to cause Excel to read beyond the intended buffer boundaries when processing certain crafted Excel files. The buffer over-read can lead to disclosure of sensitive information residing in adjacent memory areas, potentially exposing confidential data to the attacker. The vulnerability does not require any privileges (PR:N) but does require user interaction (UI:R), meaning the victim must open a maliciously crafted Excel file locally. The attack vector is local (AV:L), limiting remote exploitation possibilities. The CVSS v3.1 base score is 5.5 (medium severity), reflecting the moderate impact on confidentiality without affecting integrity or availability. No known exploits have been reported in the wild, and no official patches have been released at the time of publication. The vulnerability is significant because Microsoft Office remains widely used in enterprise environments, and local information disclosure can aid attackers in further attacks or reconnaissance. The lack of remote exploitability reduces the immediate risk but does not eliminate the threat in environments where local access can be obtained, such as through phishing or insider threats.

For European organizations, this vulnerability poses a risk primarily to confidentiality, as sensitive information could be disclosed locally by opening a malicious Excel file. This could lead to leakage of corporate data, intellectual property, or personal information, which may have regulatory implications under GDPR. Although the vulnerability does not affect integrity or availability, the information disclosure could facilitate subsequent attacks or insider threats. The requirement for local access and user interaction limits the scope of impact but does not negate the risk in environments with shared workstations, remote desktop access, or where users may be tricked into opening malicious files. Organizations in sectors with high reliance on Microsoft Office, such as finance, government, and critical infrastructure, may face higher risks. Additionally, the absence of a patch means organizations must rely on interim mitigations until an official fix is released. Failure to address this vulnerability could result in data breaches and compliance violations, impacting reputation and operational security.

1. Implement strict access controls to limit local access to systems running Microsoft Office 2019, especially in sensitive environments. 2. Educate users to recognize and avoid opening suspicious or unexpected Excel files, particularly from untrusted sources. 3. Employ endpoint security solutions capable of detecting and blocking malicious Office documents or anomalous file behaviors. 4. Use application whitelisting to restrict execution of unauthorized files and macros. 5. Monitor local system activity for unusual file access or memory usage patterns that could indicate exploitation attempts. 6. Once Microsoft releases a patch, prioritize its deployment across all affected systems to remediate the vulnerability. 7. Consider using sandboxing or isolated environments for opening untrusted Excel files to contain potential exploitation. 8. Regularly review and update security policies related to file sharing and email attachments to reduce exposure to malicious documents.