This vulnerability (CVE-2026-78439) involves a stack-based buffer overflow in the Microsoft Graphics Component used by Microsoft Office 365 for Mac. The flaw enables remote code execution by an unauthorized attacker over a network. The CVSS 3.1 base score is 8.8, indicating high severity, with attack vector network, low attack complexity, no privileges required, user interaction required, and high impact on confidentiality, integrity, and availability. Microsoft has released an official fix for this vulnerability and manages remediation for the cloud-hosted Office 365 for Mac service.

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code remotely, potentially leading to full compromise of the affected system's confidentiality, integrity, and availability. Since the vulnerability is in a widely used component of Office 365 for Mac, it poses a significant risk if unpatched.

An official fix is available from Microsoft. Because this is a cloud-hosted service, Microsoft manages the remediation server-side. Users and administrators should ensure their Office 365 for Mac installations are updated according to Microsoft’s guidance at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78439. No additional mitigation steps are required beyond applying the official update.