CVE-2026-97770: CWE-121: Stack-based Buffer Overflow in Microsoft Microsoft 365 Apps for Enterprise

This vulnerability (CVE-2026-97770) is a stack-based buffer overflow in Microsoft Office Excel, part of Microsoft 365 Apps for Enterprise. It enables remote code execution by an unauthorized attacker over a network. The CVSS 3.1 score is 8.8 (high), reflecting network attack vector, low attack complexity, no privileges required, user interaction required, and high impact on confidentiality, integrity, and availability. Multiple affected versions are identified, including exact versions and version ranges prior to specific fixed builds. Microsoft has issued an official fix and manages remediation for this cloud service. No known active exploitation has been reported.

Successful exploitation allows an attacker to execute arbitrary code remotely without privileges, potentially leading to full compromise of the affected system. The vulnerability impacts confidentiality, integrity, and availability of the system. Given the network attack vector and high impact, this represents a significant security risk if unpatched.

An official fix is available from Microsoft. Since this is a cloud-hosted service, Microsoft manages remediation server-side. Users and administrators should ensure their Microsoft 365 Apps for Enterprise installations are updated to the fixed versions as per Microsoft's advisory. No additional mitigation steps are indicated by the vendor.