CVE-2026-20870: Windows Win32 Kernel Subsystem Elevation of Privilege Vulnerability

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-01-13 · updated 2026-07-30
Weakness: CWE-416

Description

Use after free in Windows Win32K - ICOMP allows an authorized attacker to elevate privileges locally.

Affected products

Microsoft Windows 11: before 10.0.26100.7623 — fixed in 10.0.26100.7623
Microsoft Windows 11 25H2: before 10.0.26200.7623 — fixed in 10.0.26200.7623
Microsoft Windows Server 2025: before 10.0.26100.32230 — fixed in 10.0.26100.32230
Microsoft Windows 11: from 10.0.26100.0 before 10.0.26100.7623 — fixed in 10.0.26100.7623
Microsoft Windows 11 25H2: from 10.0.26200.0 before 10.0.26200.7623 — fixed in 10.0.26200.7623
Microsoft Windows Server 2025: from 10.0.26100.0 before 10.0.26100.32230 — fixed in 10.0.26100.32230

How to fix

Upgrade to a fixed version: Microsoft Windows 11 10.0.26100.7623; Microsoft Windows 11 25H2 10.0.26200.7623; Microsoft Windows Server 2025 10.0.26100.32230; Microsoft Windows 11 10.0.26100.7623; Microsoft Windows 11 25H2 10.0.26200.7623; Microsoft Windows Server 2025 10.0.26100.32230. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20870

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