CVE-2026-77898: CWE-122: Heap-based Buffer Overflow in Microsoft Microsoft 365 Apps for Enterprise

This vulnerability (CVE-2026-77898) 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, requiring no privileges but user interaction. The CVSS 3.1 vector indicates network attack vector, high attack complexity, no privileges required, user interaction required, unchanged scope, and high impact on confidentiality, integrity, and availability. Multiple version ranges of Microsoft 365 Apps for Enterprise prior to specific builds are affected. Microsoft has published an official fix for this vulnerability.

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code remotely, potentially leading to full compromise of the affected system. The impact includes high confidentiality, integrity, and availability losses. However, exploitation requires user interaction and has high attack complexity.

An official fix is available from Microsoft. Users and administrators should apply the security updates provided by Microsoft as detailed in the vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-77898. Since this is a cloud service, Microsoft manages remediation for the cloud-hosted components. No known exploits are reported in the wild at this time.