An integer underflow (wrap or wraparound) vulnerability identified as CVE-2026-45469 exists in Microsoft Office Excel, part of Microsoft 365 Apps for Enterprise. This vulnerability allows an unauthorized attacker to execute code locally by exploiting the integer underflow condition. The CVSS v3.1 base score is 7.8, indicating high severity, with attack vector local, low attack complexity, no privileges required, and user interaction required. 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 with high impact on confidentiality, integrity, and availability. This means an attacker could run arbitrary code on the affected system, potentially leading to full compromise of the local environment.

Microsoft has released an official fix for CVE-2026-45469. Since this is a cloud-hosted service, Microsoft manages remediation server-side. Users and administrators should ensure that their 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-2026-45469. No additional mitigation steps are required beyond applying the official fix.