Buffer overflow in Microsoft 365 Apps For Enterprise
CVE-2026-20957
Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
EPSS: 0.002 (36.7th 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/E:U/RL:O/RC:C.
Affected products
- 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 Online Server — versions 16.0.0.0
Weakness classification (CWE)
References
- Microsoft Excel Remote Code Execution Vulnerability (vendor-advisory, patch)
Frequently asked questions
- What is CVE-2026-20957?
- CVE-2026-20957 is a high-severity vulnerability in Microsoft 365 Apps For Enterprise, classified under Integer Underflow. CVSS score: 7.8/10. Published 2026-01-13.
- How severe is CVE-2026-20957?
- High severity. CVSS v3 base score is 7.8 out of 10.