CVE-2026-26166: Windows Shell Elevation of Privilege Vulnerability

Severity: high (CVSS 7.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-14 · updated 2026-10-26
Weakness: CWE-415

Description

Double free in Windows Shell allows an authorized attacker to elevate privileges locally.

Affected products

Microsoft Windows 11: before 10.0.22631.6936 — fixed in 10.0.22631.6936
Microsoft Windows 11: before 10.0.26100.8246 — fixed in 10.0.26100.8246
Microsoft Windows 11 25H2: before 10.0.26200.8246 — fixed in 10.0.26200.8246
Microsoft Windows 11 version 26H1: before 10.0.28000.1836 — fixed in 10.0.28000.1836
Microsoft Windows Server 2022: before 10.0.20348.5020 — fixed in 10.0.20348.5020
Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): before 10.0.25398.2274 — fixed in 10.0.25398.2274
Microsoft Windows Server 2025: before 10.0.26100.32690 — fixed in 10.0.26100.32690
Microsoft Windows 11: from 10.0.22631.0 before 10.0.22631.6936 — fixed in 10.0.22631.6936
Microsoft Windows 11: from 10.0.26100.0 before 10.0.26100.8246 — fixed in 10.0.26100.8246
Microsoft Windows 11 25H2: from 10.0.26200.0 before 10.0.26200.8246 — fixed in 10.0.26200.8246
Microsoft Windows 11 version 26H1: from 10.0.28000.0 before 10.0.28000.1836 — fixed in 10.0.28000.1836
Microsoft Windows Server 2022: from 10.0.20348.0 before 10.0.20348.5020 — fixed in 10.0.20348.5020
Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): from 10.0.25398.0 before 10.0.25398.2274 — fixed in 10.0.25398.2274
Microsoft Windows Server 2025: from 10.0.26100.0 before 10.0.26100.32690 — fixed in 10.0.26100.32690

How to fix

Upgrade to a fixed version: Microsoft Windows 11 10.0.22631.6936; Microsoft Windows 11 10.0.26100.8246; Microsoft Windows 11 25H2 10.0.26200.8246; Microsoft Windows 11 version 26H1 10.0.28000.1836; Microsoft Windows Server 2022 10.0.20348.5020; Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.2274; Microsoft Windows Server 2025 10.0.26100.32690; Microsoft Windows 11 10.0.22631.6936; Microsoft Windows 11 10.0.26100.8246; Microsoft Windows 11 25H2 10.0.26200.8246; Microsoft Windows 11 version 26H1 10.0.28000.1836; Microsoft Windows Server 2022 10.0.20348.5020. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26166

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