CVE-2026-78517: CWE-122: Heap-based Buffer Overflow in Microsoft Microsoft 365 Apps for Enterprise

This vulnerability (CVE-2026-78517) involves a heap-based buffer overflow in Microsoft Office Word, part of Microsoft 365 Apps for Enterprise. It enables remote code execution by an unauthorized attacker over a network. The CVSS v3.1 base score is 8.8, reflecting high impact on confidentiality, integrity, and availability. The vulnerability affects several version ranges of Microsoft 365 Apps for Enterprise prior to fixed versions. Microsoft has released an official fix and manages remediation for this cloud service. No known exploits are reported in the wild at this time.

Successful exploitation could allow an attacker to execute arbitrary code remotely, potentially leading to full compromise of the affected system. The vulnerability impacts confidentiality, integrity, and availability with high severity. However, there are no known active exploits in the wild currently.

An official fix is available from Microsoft. Users and administrators should apply the provided updates as detailed in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78517. Since this is a cloud-hosted service, Microsoft manages remediation server-side. Check the vendor advisory for the latest remediation status and guidance.