CVE-2026-55058 is an out-of-bounds read vulnerability (CWE-125) in Microsoft Office Excel component of Microsoft 365 Apps for Enterprise. It allows an unauthorized attacker to execute code locally by exploiting improper bounds checking. The vulnerability has a CVSS 3.1 base score of 7.8 (high severity) with attack vector local, low attack complexity, no privileges required, user interaction required, and impacts confidentiality, integrity, and availability. Microsoft has published an official fix and manages remediation for this cloud service. No active exploitation has been reported.

Successful exploitation of this vulnerability could lead to local code execution by an unauthorized attacker, potentially compromising confidentiality, integrity, and availability of the affected system. The CVSS score of 7.8 indicates a high impact. However, exploitation requires local access and user interaction.

An official fix is available from Microsoft. Since this is a cloud-hosted service, Microsoft manages the remediation server-side. Users and administrators should ensure that Microsoft 365 Apps for Enterprise are updated to the fixed version as per Microsoft's advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55058. No additional mitigation actions are required beyond applying the official fix.