CVE-2026-55031 Details

A vulnerability allowing out-of-bounds read has been identified in Microsoft Office Excel. This issue enables an unauthorized attacker to execute code locally. The vulnerability is present in several versions of Microsoft Excel, including Excel 2016 (both 32-bit and 64-bit editions), Microsoft Office LTSC for Mac 2021 and 2024 (both 32-bit and 64-bit editions), Microsoft Office LTSC 2021 (both 32-bit and 64-bit editions), Microsoft Office 2019 (both 32-bit and 64-bit editions), Microsoft 365 Apps for Enterprise (both 32-bit and 64-bit systems), and Office Online Server.

Users can download the security update for Microsoft Excel 2016 (32-bit and 64-bit editions) from the Microsoft Update Catalog. For Microsoft Office LTSC for Mac 2021 and 2024, security updates are also available through the Mac App Store. Microsoft 365 Apps for Enterprise users can download the security update via the Office Update mechanism. Office Online Server users can download the security update from the Microsoft Update Catalog.