CVE-2026-21249: Microsoft Windows 10 1607

Low severity, CVSS 3.3. EPSS: 11.4% chance of exploitation in the next 30 days.

External control of file name or path in Windows NTLM allows an unauthorized attacker to perform spoofing locally.

Affected products

• Microsoft Windows 10 1607: before 10.0.14393.8868 (fixed in 10.0.14393.8868)
• Microsoft Windows 10 1809: before 10.0.17763.8389 (fixed in 10.0.17763.8389)
• Microsoft Windows 10 21h2: before 10.0.19044.6937 (fixed in 10.0.19044.6937)
• Microsoft Windows 10 22h2: before 10.0.19045.6937 (fixed in 10.0.19045.6937)
• Microsoft Windows 11 23h2: before 10.0.22631.6649 (fixed in 10.0.22631.6649)
• Microsoft Windows 11 24h2: before 10.0.26100.7781 (fixed in 10.0.26100.7781)
• Microsoft Windows 11 25h2: before 10.0.26200.7781 (fixed in 10.0.26200.7781)
• Microsoft Windows Server 2012: version r2 only
• Microsoft Windows Server 2016: before 10.0.14393.8868 (fixed in 10.0.14393.8868)
• Microsoft Windows Server 2019: before 10.0.17763.8389 (fixed in 10.0.17763.8389)
• Microsoft Windows Server 2022: before 10.0.20348.4711 (fixed in 10.0.20348.4711)
• Microsoft Windows Server 2022 23h2: before 10.0.25398.2149 (fixed in 10.0.25398.2149)
• Microsoft Windows Server 2025: before 10.0.26100.32313 (fixed in 10.0.26100.32313)

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