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PatchSiren cyber security CVE debrief

CVE-2026-62775 Microsoft CVE debrief

A vulnerability in the Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized local attacker to disclose information. Microsoft has released a patch for this vulnerability affecting Windows 11 version 26H1. The vulnerability is related to incorrect authorization in the Windows Container Isolation FS Filter Driver (unionfs.sys), which enables an authorized attacker to disclose information locally. System administrators and security teams should assess exposure and apply patches. This vulnerability has a CVSS score of 5.5 and a severity of MEDIUM.

Vendor
Microsoft
Product
Windows 11 version 26H1
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-08-11
Original CVE updated
2026-10-08
Advisory published
2026-08-11
Advisory updated
2026-10-08

Who should care

System administrators and security teams responsible for Windows 11 version 26H1 systems should assess exposure and apply patches. This vulnerability has a CVSS score of 5.5 and a severity of MEDIUM, indicating a moderate level of risk. Affected operators, platforms, and vulnerability management teams should review the official advisory and CVE record to validate affected scope, severity, and vendor guidance.

Why it matters

This vulnerability in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized local attacker to disclose information. System administrators and security teams should assess exposure, apply patches, and monitor system logs.

  • Potential information disclosure on affected systems
  • Need to verify system configurations and apply patches
  • Monitoring system logs for potential information disclosure attempts

Technical summary

The Windows Container Isolation FS Filter Driver (unionfs.sys) has a vulnerability that allows an authorized local attacker to disclose information. This vulnerability affects Windows 11 version 26H1 and has a CVSS score of 5.5. The vulnerability is related to incorrect authorization in the Windows Container Isolation FS Filter Driver (unionfs.sys). Microsoft has released a patch for this vulnerability.

Defensive priority

Apply patches for Windows 11 version 26H1 immediately, especially for systems with high security requirements.

Recommended defensive actions

  • Apply patches for Windows 11 version 26H1
  • Review system configurations for Windows 11 version 26H1
  • Monitor system logs for potential information disclosure attempts

Evidence notes

The CVE record and Microsoft's advisory confirm the vulnerability in Windows Container Isolation FS Filter Driver (unionfs.sys). The vulnerability affects Windows 11 version 26H1 and has a CVSS score of 5.5. The CVE record was published on 2026-08-11T17:06:11.630Z and has not been modified since then. The official CVE Program record and NIST NVD detail page provide additional information on the vulnerability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-62775 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-62775

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

  • CVE-2026-62775 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-62775

    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.