Vulnerability in Microsoft 365 Apps
CVE-2026-40420
Use after free in Microsoft Office allows an authorized attacker to elevate privileges locally.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.003 (21.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 21st percentile — 21.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
- Microsoft 365 Apps
- Microsoft 365 Apps For Enterprise — versions 16.0.1
- 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 — versions 2019
- Microsoft Office Long Term Servicing Channel — versions 2021, 2024
Weakness classification (CWE)
References
- Microsoft Office Click-To-Run Elevation of Privilege Vulnerability (vendor-advisory, patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-40420?
- CVE-2026-40420 is a high-severity vulnerability in Microsoft 365 Apps, classified under Improper Access Control. CVSS score: 8.8/10. Published 2026-05-12.
- How severe is CVE-2026-40420?
- High severity. CVSS v3 base score is 8.8 out of 10.