This vulnerability is a stack-based buffer overflow (CWE-121) in Microsoft Office Excel, part of Microsoft 365 Apps for Enterprise. It enables an unauthorized attacker to execute arbitrary code locally by exploiting the overflow condition. The affected version is exactly 16.0.1. The vulnerability has been assigned CVE-2026-81953 and has a CVSS 3.1 base score of 7.8, indicating high impact on confidentiality, integrity, and availability. Microsoft has issued an official fix and manages remediation for this cloud-hosted service. No active exploitation has been reported.

Successful exploitation allows unauthorized local code execution, potentially leading to full compromise of the affected system's confidentiality, integrity, and availability. Given the local attack vector and user interaction requirement, the risk is significant but requires local access and user action.

An official fix is available from Microsoft. Users and administrators should apply the provided update to Microsoft 365 Apps for Enterprise version 16.0.1 as soon as possible. Since this is a cloud service, Microsoft manages remediation server-side; verify with the Microsoft Security Response Center advisory for the latest update status and deployment guidance.