This vulnerability (CVE-2026-56156) is a heap-based buffer overflow in Microsoft Office Excel as 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 base score is 7.8, reflecting high impact with local attack vector, low attack complexity, no privileges required, and user interaction needed. Microsoft has published an official fix and manages remediation for this cloud service. No known exploits are reported in the wild at this time.

Successful exploitation allows an attacker to execute arbitrary code locally, resulting in complete compromise of the affected system's confidentiality, integrity, and availability. This could lead to unauthorized actions and potential system takeover.

An official fix is available from Microsoft. Since this is a cloud-hosted service, Microsoft manages the remediation server-side. Users and administrators should follow the guidance in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56156 to ensure their environments are updated and protected.