CVE-2026-21261: Microsoft 365 Apps

Medium severity, CVSS 5.5. EPSS: 0.6% chance of exploitation in the next 30 days.

Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information 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 16.0.10417.20097 (fixed in 16.0.10417.20097)

Published 2026-02-10. Last modified 2026-06-17.