CVE-2025-59231: 
vulnerability analysis and mitigation

Access of resource using incompatible type ('type confusion') in Microsoft Office Excel allows an unauthorized attacker to execute code locally. This vulnerability (CVE-2025-59231) was disclosed on October 14, 2025. The affected systems include Microsoft Excel 2016, Microsoft Office 2019, Microsoft 365 Apps for Enterprise, Microsoft Office LTSC 2021/2024 (both Windows and Mac versions), and Office Online Server (NVD).

The vulnerability is classified as a type confusion issue (CWE-843) that could lead to code execution. It has received a CVSS v3.1 base score of 7.8 (HIGH), with the following vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. The scoring indicates that while the attack vector is local and requires user interaction, it needs no privileges and can result in high impacts to confidentiality, integrity, and availability (NVD, AttackerKB).

The vulnerability can lead to high impacts across confidentiality, integrity, and availability of the affected system. If successfully exploited, it allows an unauthorized attacker to execute code locally on the affected system (NVD).

Microsoft has released security updates to address this vulnerability. The fixes are available through Microsoft Update, Microsoft Update Catalog, and Microsoft Download Center. For Excel 2016, the security update KB5002794 has been released, while for Office Online Server, the security update KB5002797 addresses this vulnerability (Microsoft Support).