CVE-2026-78510A remote code execution vulnerability exists when Microsoft Office improperly validates input before loading dynamic link library (DLL) files. An attacker who successfully exploited this vulnerability could take control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
To exploit the vulnerability, an attacker must first convince a user to open a specially crafted Office document.
The updates address the vulnerability by correcting how Office validates input before loading DLL files.