CVE-2026-78505: CWE-122: Heap-based Buffer Overflow in Microsoft Microsoft 365 Apps for Enterprise

This vulnerability (CVE-2026-78505) is a heap-based buffer overflow in Microsoft 365 Apps for Enterprise, enabling remote code execution by an unauthorized attacker. The flaw allows code execution over a network without requiring privileges but does require user interaction. The vulnerability affects several version ranges of Microsoft 365 Apps for Enterprise prior to the fixed versions. Microsoft has published an official security update to address this issue.

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code with high impact on confidentiality, integrity, and availability. The attacker can remotely execute code without privileges but requires user interaction. This could lead to full compromise of the affected system.

An official fix is available from Microsoft. Users and administrators should apply the security updates provided by Microsoft for Microsoft 365 Apps for Enterprise as detailed in the Microsoft Security Response Center advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78505. Since this is a cloud-hosted service, Microsoft manages remediation for the cloud environment. For on-premises or client installations, patching is required.