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PatchSiren cyber security CVE debrief

CVE-2026-40409 Microsoft CVE debrief

CVE-2026-40409 is a HIGH severity Elevation of Privilege vulnerability in the Windows Universal Disk Format File System Driver (UDFS). The vulnerability has a CVSS score of 7.8 and was published on 2026-06-09T17:17:06.417Z. The vulnerability affects multiple versions of Windows 10, Windows 11, and Windows Server.

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-09
Original CVE updated
2026-06-11
Advisory published
2026-06-09
Advisory updated
2026-06-11

Who should care

Administrators and users of affected Windows systems should prioritize patching this vulnerability to prevent potential elevation of privilege attacks.

Technical summary

The vulnerability exists in the Windows Universal Disk Format File System Driver (UDFS) and allows an attacker to elevate their privileges on a vulnerable system. The vulnerability has been assigned a CVSS score of 7.8 and a CVSS vector of CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Defensive priority

High

Recommended defensive actions

  • Apply the security patch from Microsoft as soon as possible.
  • Ensure that all affected systems are updated with the latest security patches.
  • Consider implementing additional security measures, such as monitoring system logs and network activity, to detect potential attacks.

Evidence notes

The vulnerability is described in the CVE-2026-40409 CVE record [cve-org] and detailed in the NVD vulnerability database [nvd]. Microsoft has provided a vendor advisory for this vulnerability [ref-4].

Sources and references

Verified primary and authoritative sources

  • CVE-2026-40409 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-40409

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-40409 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-40409

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.