CVE-2026-40359: Microsoft 365 Apps

High severity, CVSS 7.8. EPSS: 0.5% chance of exploitation in the next 30 days.

Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

Affected products

• Microsoft 365 Apps: affected versions not specified
• Microsoft Excel: version 2016 only
• Microsoft Office: version 2019 only
• Microsoft Office Long Term Servicing Channel: version 2021 only; version 2024 only
• Microsoft Office Online Server: before 16.0.10417.20128 (fixed in 16.0.10417.20128)

Published 2026-05-12. Last modified 2026-06-17.