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CVE-2026-27918 Microsoft CVE debrief

A race condition vulnerability in Windows Shell allows an authorized attacker to elevate privileges locally. Multiple Windows versions are affected, including Windows 10, Windows 11, and Windows Server. This vulnerability has significant implications for defenders who manage Windows systems, as it can be exploited locally to gain elevated privileges. The vulnerability is a result of improper synchronization in Windows Shell, which allows an attacker to execute code with higher privileges. Defenders should assess exposure, apply patches, and monitor for suspicious activity.

Vendor
Microsoft
Product
Windows 10 Version 1809
CVSS
HIGH 7.8
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 responsible for Windows systems, particularly those managing Windows 10, Windows 11, and Windows Server environments, should assess exposure and apply patches.

Why it matters

CVE-2026-27918 is a high-severity vulnerability in Windows Shell that allows local privilege elevation. Defenders should assess exposure, apply patches, and monitor for suspicious activity.

  • Local privilege elevation is possible
  • Authorized attackers can exploit the vulnerability
  • Patching is required for affected versions
  • Monitoring for suspicious activity is recommended

Technical summary

A race condition vulnerability in Windows Shell allows an authorized attacker to elevate privileges locally. The vulnerability affects multiple Windows versions, including Windows 10, Windows 11, and Windows Server. The vulnerability is caused by improper synchronization in Windows Shell, which allows an attacker to execute code with higher privileges. The vulnerability has a high CVSS score of 7.8 and is considered a high-severity vulnerability.

Defensive priority

High

Recommended defensive actions

  • Assess exposure for Windows 10, Windows 11, and Windows Server systems
  • Verify and apply Microsoft patches for affected versions
  • Monitor for local privilege elevation attempts
  • Review system logs for suspicious activity

Evidence notes

The CVE Program and NVD provide official records of the vulnerability. Microsoft has released a patch for the vulnerability. The vulnerability affects multiple Windows versions, including Windows 10, Windows 11, and Windows Server. The CVE record was published on 2026-04-14T16:57:12.691Z and has not been modified since then. There is no evidence of public exploitation or widespread attacks.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-27918 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-27918

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

  • CVE-2026-27918 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-27918

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

Supplemental references

  • Windows Shell Elevation of Privilege Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/27xxx/CVE-2026-27918.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-27918

    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.