CVE-2026-55029 Details

A heap-based buffer overflow vulnerability has been identified in Microsoft Office Excel. This vulnerability allows an unauthorized attacker to execute code locally. It affects multiple versions of Excel, including Excel 2016 (both 32-bit and 64-bit editions), Excel LTSC 2021 (32-bit and 64-bit editions), Excel LTSC for Mac 2021, and Excel LTSC for Mac 2024. The vulnerability arises from a heap-based buffer overflow, which can be exploited by sending a malicious Office file to a user and convincing them to open it.

Users can download the security update for this vulnerability through the Microsoft Update Catalog. For Office 365 for Mac, the update is available via the Microsoft 365 for Mac update channel. Instructions for downloading the update can be found in the Microsoft 365 Apps Security Updates documentation.