CVE-2026-40409

CVE-2026-40409 is a high-severity vulnerability in Microsoft Windows 10 1607 with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-197.

Key facts

• Severity: High (CVSS 3.x base score 7.8)
• EPSS exploit prediction: 0% (22nd percentile)
• Actively exploited: Not listed in CISA KEV
• EU (EUVD) id: EUVD-2026-35655
• Weakness: CWE-197
• Affected product: Microsoft Windows 10 1607
• Published: 2026-06-09
• Last modified: 2026-06-17

Description

Windows Universal Disk Format File System Driver (UDFS) Elevation of Privilege Vulnerability

Frequently asked questions

What is CVE-2026-40409?

Windows Universal Disk Format File System Driver (UDFS) Elevation of Privilege Vulnerability

How severe is CVE-2026-40409?

CVE-2026-40409 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-40409 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40409?

CVE-2026-40409 primarily affects Microsoft Windows 10 1607. In total, 24 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-40409?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-40409 have an EU (EUVD) identifier?

Yes. CVE-2026-40409 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35655.

When was CVE-2026-40409 published?

CVE-2026-40409 was published on 2026-06-09 and last updated on 2026-06-17.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40409

Affected products (24)

• cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*
• cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*
• cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*
• cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*
• cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:arm64:*
• cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x64:*
• cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x86:*
• cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:arm64:*
• cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x64:*
• cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x86:*
• cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:arm64:*
• cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:x64:*
• cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:arm64:*
• cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:x64:*
• cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:arm64:*
• cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:x64:*
• cpe:2.3:o:microsoft:windows_11_26h1:*:*:*:*:*:*:arm64:*
• cpe:2.3:o:microsoft:windows_11_26h1:*:*:*:*:*:*:x64:*
• cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*
• cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:x64:*

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