This vulnerability (CWE-122) involves a heap-based buffer overflow in Microsoft Office Word, part of Microsoft 365 Apps for Enterprise. Exploitation can lead to remote code execution by an attacker without privileges but requires user interaction. The CVSS 3.1 base score is 8.8, reflecting high impact on confidentiality, integrity, and availability. Microsoft has published an official fix and manages remediation for this cloud service. No known exploits are currently reported in the wild.

Successful exploitation allows an attacker to execute arbitrary code remotely, potentially leading to full compromise of affected systems. The vulnerability affects confidentiality, integrity, and availability with high impact. User interaction is required for exploitation, and no active exploits are known at this time.

An official fix is available from Microsoft. Since this is a cloud-hosted service, Microsoft manages remediation server-side. Users and administrators should apply the official update as directed in the Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78521 to mitigate this vulnerability.