CVE-2026-78504: CWE-121: Stack-based Buffer Overflow in Microsoft Microsoft 365 Apps for Enterprise

This vulnerability, identified as CVE-2026-78504 and classified under CWE-121 (stack-based buffer overflow), affects Microsoft Office Word in Microsoft 365 Apps for Enterprise. It enables remote code execution by an unauthorized attacker due to a stack-based buffer overflow condition. The CVSS 3.1 base score is 8.8, indicating high severity with network attack vector, low attack complexity, no privileges required, and user interaction required. Microsoft has published an official fix for this vulnerability and manages remediation for the cloud-hosted service. No active exploitation has been reported.

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code remotely with high impact on confidentiality, integrity, and availability. This could lead to full compromise of the affected system running Microsoft 365 Apps for Enterprise Word component.

An official fix is available from Microsoft. Users and administrators should apply the security updates provided by Microsoft as detailed in the vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78504. Since this is a cloud service, Microsoft manages remediation for the cloud-hosted components. There are no known exploits in the wild, but timely patching is recommended.