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CVE-2026-0390 Microsoft CVE debrief

The CVE-2026-0390 vulnerability is a UEFI Secure Boot Security Feature Bypass issue affecting multiple Windows versions. An authorized attacker could bypass a security feature locally due to reliance on untrusted inputs in a security decision in the Windows Boot Loader. This medium-severity vulnerability allows defenders to assess exposure and apply patches. The CVE record and source item provide details on the vulnerability, affected products, and references to vendor advisories. However, specific details on exploitation are limited. Defenders managing Windows systems, especially those responsible for patch management, vulnerability assessment, and UEFI Secure Boot configurations,

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
MEDIUM 6.7
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-14
Original CVE updated
2026-10-15
Advisory published
2026-04-14
Advisory updated
2026-10-15

Who should care

Defenders managing Windows systems, especially those responsible for patch management, vulnerability assessment, and UEFI Secure Boot configurations, should assess exposure and apply patches.

Why it matters

CVE-2026-0390 is a medium-severity vulnerability in the Windows Boot Loader that allows an authorized attacker to bypass UEFI Secure Boot locally. Defenders should assess exposure, apply patches, and verify UEFI Secure Boot configurations to prevent potential security feature bypasses.

  • Defenders need to verify if their Windows systems are affected and apply patches to prevent local security feature bypass.
  • System administrators should review UEFI Secure Boot configurations to ensure they are properly set up.
  • Security teams must prioritize patching for Windows versions 1607, 1809, 21H2, 22H2, and affected Windows Server versions.
  • Incident response teams should be prepared to investigate potential bypass attempts

Technical summary

The vulnerability (CVE-2026-0390) is caused by the Windows Boot Loader's reliance on untrusted inputs for security decisions, allowing an authorized attacker to bypass UEFI Secure Boot locally. Affected products include Windows 10 versions 1607, 1809, 21H2, 22H2, and various Windows Server versions.

Defensive priority

Medium priority for defenders, especially those managing Windows systems, to assess exposure and apply patches.

Recommended defensive actions

  • Assess exposure of Windows systems to CVE-2026-0390
  • Apply patches from Microsoft for affected Windows versions
  • Verify UEFI Secure Boot configuration
  • Monitor system logs for potential bypass attempts

Evidence notes

The CVE record and source item provide details on the vulnerability, affected products, and references to vendor advisories. However, specific details on exploitation are limited.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-0390 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-0390

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

  • CVE-2026-0390 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-0390

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

Supplemental references

  • UEFI Secure Boot Security Feature Bypass Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/0xxx/CVE-2026-0390.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-0390

    Supplemental source - vendor-advisory, patch

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.