CVE-2026-69617: Microsoft Windows 11 26h1

High severity, CVSS 7.0. EPSS: 0.3% chance of exploitation in the next 30 days.

Out-of-bounds read in Windows Resilient File System (ReFS) allows an authorized attacker to elevate privileges locally.

Affected products

• Microsoft Windows 11 26h1: before 10.0.28000.2954 (fixed in 10.0.28000.2954)
• Microsoft Windows Server 2025: before 10.0.26100.33438 (fixed in 10.0.26100.33438)

Published 2026-09-08. Last modified 2026-09-21.