CVE-2026-26134: Microsoft 365 Copilot

High severity, CVSS 7.8. EPSS: 0.3% chance of exploitation in the next 30 days.

Integer overflow or wraparound in Microsoft Office allows an authorized attacker to elevate privileges locally.

Affected products

• Microsoft 365 Copilot: before 16.0.19822.20000 (fixed in 16.0.19822.20000)

Published 2026-03-10. Last modified 2026-06-17.