Out-of-bounds Read in Microsoft 365_apps
CVE-2026-21258
Improper input validation in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
EPSS: 0.006 (44.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.
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
- secure@microsoft.com (vendor-advisory, patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-21258?
- CVE-2026-21258 is a medium-severity vulnerability in Microsoft 365_apps, classified under Improper Input Validation. CVSS score: 5.5/10. Published 2026-02-10.
- How severe is CVE-2026-21258?
- Medium severity. CVSS v3 base score is 5.5 out of 10.