7.8
High
CVE-2026-21259 Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges locally
Description
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges locally.
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| Office Online Server 16.0 | 16.0.0.0 → < 16.0.10417.20097 | 16.0.10417.20097 |
| Microsoft Office 2019 19.0 | 19.0.0 → latest | No fix stated |
| Microsoft 365 Apps for Enterprise 16.0 | 16.0.1 → latest | No fix stated |
| Microsoft Office LTSC 2021 16.0 | 16.0.1 → latest | No fix stated |
| Microsoft Office LTSC 2024 16.0 | 16.0.0 → latest | No fix stated |
| Microsoft Excel 2016 16.0 | 16.0.0.0 → < 16.0.5539.1002 | 16.0.5539.1002 |
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