CVE-2026-81390: CWE-125: Out-of-bounds Read in Microsoft Microsoft 365 Apps for Enterprise

This vulnerability (CVE-2026-81390) involves an out-of-bounds read in Microsoft Office Excel, part of Microsoft 365 Apps for Enterprise. It enables an unauthorized attacker to disclose information locally by reading memory outside the intended bounds. The CVSS 3.1 base score is 5.5, reflecting medium severity with local attack vector, low complexity, no privileges required, and user interaction needed. The vulnerability affects multiple versions of Microsoft 365 Apps for Enterprise prior to various fixed builds as specified. Microsoft has issued an official fix and manages remediation for this cloud service. No active exploitation has been reported.

An attacker can cause an out-of-bounds read in Excel, leading to local information disclosure. This does not allow code execution or denial of service but may expose sensitive data accessible in memory. The impact is limited to local information disclosure without integrity or availability impact.

An official fix is available from Microsoft. Since this is a cloud-hosted service, Microsoft manages remediation server-side. Users and administrators should apply the official updates as directed in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-81390 to mitigate this vulnerability.