This vulnerability (CVE-2026-44818) in Microsoft 365 Apps for Enterprise arises from an integer underflow in Microsoft Office Excel, categorized under CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization). The flaw allows unauthorized local code execution due to improper handling of shared resources leading to a race condition. The CVSS 3.1 base score is 7.0, indicating high severity, with attack vector local, high attack complexity, no privileges required, and user interaction required. Microsoft has published an official fix and manages remediation for this cloud service. The affected version explicitly identified is 16.0.1.

Successful exploitation of this vulnerability could allow an unauthorized attacker to execute arbitrary code locally on the affected system, potentially leading to full compromise of the application and associated data. The vulnerability impacts confidentiality, integrity, and availability, all rated high. However, exploitation requires local access and user interaction, and the attack complexity is high.

An official fix is available from Microsoft. Since this is a cloud-hosted service, Microsoft manages remediation server-side. Users and administrators should ensure that their Microsoft 365 Apps for Enterprise environment is updated to the fixed version as per Microsoft's guidance in the advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44818. No additional mitigation actions are indicated by the vendor advisory.