CVE-2026-40422: Windows File Explorer Information Disclosure Vulnerability

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-14 · updated 2026-10-28
Weakness: CWE-908

Description

Use of uninitialized resource in Windows File Explorer allows an authorized attacker to disclose information locally.

Affected products

Microsoft Windows 10 1607: before 10.0.14393.9339 — fixed in 10.0.14393.9339
Microsoft Windows 10: before 10.0.17763.9020 — fixed in 10.0.17763.9020
Microsoft Windows 10: before 10.0.19044.7548 — fixed in 10.0.19044.7548
Microsoft Windows 10: before 10.0.19045.7548 — fixed in 10.0.19045.7548
Microsoft Windows 11: before 10.0.26100.8875 — fixed in 10.0.26100.8875
Microsoft Windows 11 25H2: before 10.0.26200.8875 — fixed in 10.0.26200.8875
Microsoft Windows 11 version 26H1: before 10.0.28000.2269 — fixed in 10.0.28000.2269
Microsoft Windows Server 2016: before 10.0.14393.9339 — fixed in 10.0.14393.9339
Microsoft Windows Server 2019: before 10.0.17763.9020 — fixed in 10.0.17763.9020
Microsoft Windows Server 2022: before 10.0.20348.5386 — fixed in 10.0.20348.5386
Microsoft Windows Server 2025: before 10.0.26100.33158 — fixed in 10.0.26100.33158
Microsoft Windows 10 1607: from 10.0.14393.0 before 10.0.14393.9339 — fixed in 10.0.14393.9339
Microsoft Windows 10: from 10.0.17763.0 before 10.0.17763.9020 — fixed in 10.0.17763.9020
Microsoft Windows 10: from 10.0.19044.0 before 10.0.19044.7548 — fixed in 10.0.19044.7548
Microsoft Windows 10: from 10.0.19045.0 before 10.0.19045.7548 — fixed in 10.0.19045.7548
Microsoft Windows 11: from 10.0.26100.0 before 10.0.26100.8875 — fixed in 10.0.26100.8875
Microsoft Windows 11 25H2: from 10.0.26200.0 before 10.0.26200.8875 — fixed in 10.0.26200.8875
Microsoft Windows 11 version 26H1: from 10.0.28000.0 before 10.0.28000.2525 — fixed in 10.0.28000.2525
Microsoft Windows Server 2016: from 10.0.14393.0 before 10.0.14393.9339 — fixed in 10.0.14393.9339
Microsoft Windows Server 2019: from 10.0.17763.0 before 10.0.17763.9020 — fixed in 10.0.17763.9020
Microsoft Windows Server 2022: from 10.0.20348.0 before 10.0.20348.5386 — fixed in 10.0.20348.5386
Microsoft Windows Server 2025: from 10.0.26100.0 before 10.0.26100.33158 — fixed in 10.0.26100.33158

How to fix

Upgrade to a fixed version: Microsoft Windows 10 1607 10.0.14393.9339; Microsoft Windows 10 10.0.17763.9020; Microsoft Windows 10 10.0.19044.7548; Microsoft Windows 10 10.0.19045.7548; Microsoft Windows 11 10.0.26100.8875; Microsoft Windows 11 25H2 10.0.26200.8875; Microsoft Windows 11 version 26H1 10.0.28000.2269; Microsoft Windows Server 2016 10.0.14393.9339; Microsoft Windows Server 2019 10.0.17763.9020; Microsoft Windows Server 2022 10.0.20348.5386; Microsoft Windows Server 2025 10.0.26100.33158; Microsoft Windows 10 1607 10.0.14393.9339. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40422

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