Use After Free in Microsoft 365_apps
CVE-2026-40359
Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
Vulnerability class: Use-After-Free
EPSS: 0.001 (19.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.
Affected products
- Microsoft 365_apps
- Microsoft Excel — versions 2016
- Microsoft 365 Apps For Enterprise — versions 16.0.1
- Microsoft Excel 2016 — versions 16.0.0.0
- Microsoft Office 2019 — versions 19.0.0
- Microsoft Office Ltsc 2021 — versions 16.0.1
- Microsoft Office Ltsc 2024 — versions 16.0.0
- Microsoft Office Ltsc For Mac 2021 — versions 16.0.1
- Microsoft Office Ltsc For Mac 2024 — versions 16.0.0
- Microsoft Office — versions 2019
Weakness classification (CWE)
References
- Microsoft Excel Remote Code Execution Vulnerability (vendor-advisory, patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-40359?
- CVE-2026-40359 is a high-severity vulnerability in Microsoft 365_apps, classified under Use After Free. CVSS score: 7.8/10. Published 2026-05-12.
- How severe is CVE-2026-40359?
- High severity. CVSS v3 base score is 7.8 out of 10.