Out-of-bounds Read in Microsoft 365 Apps
CVE-2026-55898
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
Vulnerability class: Buffer Overflow
EPSS: 0.005 (38.9th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H.
Affected products
- Microsoft 365_apps
- Microsoft Excel — versions 2016
- Microsoft Microsoft_365
- 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 365 For Mac — versions 1.0.0
- 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
Weakness classification (CWE)
References
- Microsoft Excel Information Disclosure Vulnerability (vendor-advisory, patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-55898?
- CVE-2026-55898 is a medium-severity vulnerability in Microsoft 365 Apps, classified under Out-of-bounds Read. CVSS score: 6.1/10. Published 2026-07-14.
- How severe is CVE-2026-55898?
- Medium severity. CVSS v3 base score is 6.1 out of 10.