CVE-2026-81397: CWE-122: Heap-based Buffer Overflow in Microsoft Microsoft 365 Apps for Enterprise

This vulnerability (CVE-2026-81397) is a heap-based buffer overflow in Microsoft Office Excel, part of Microsoft 365 Apps for Enterprise. It enables an unauthorized attacker to execute code locally, potentially leading to full compromise of confidentiality, integrity, and availability. The CVSS 3.1 vector indicates local attack vector with low complexity, no privileges required, but user interaction is needed. Microsoft has published an official fix and manages remediation for this cloud service. Multiple affected version ranges are identified, all prior to specific fixed builds.

Successful exploitation allows local code execution by an unauthorized attacker, resulting in complete compromise of the affected system's confidentiality, integrity, and availability. This could lead to arbitrary code running with user privileges.

An official fix is available from Microsoft. Users and administrators should apply the latest updates for Microsoft 365 Apps for Enterprise as detailed in the Microsoft security update guide. Since this is a cloud-hosted service, Microsoft manages remediation server-side. Check the vendor advisory for the latest patch status and update instructions.