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CVE-2026-70303 Microsoft CVE debrief

A Windows Kernel Elevation of Privilege Vulnerability exists due to an out-of-bounds write in the Windows Kernel. This allows an authorized attacker to elevate privileges locally. Multiple Windows versions and editions are affected, including Windows 10, Windows 11, and Windows Server. The vulnerability has a high severity with a CVSS score of 7.8. System administrators and security teams should assess exposure and apply patches. Review system configurations to ensure least privilege access and monitor systems for unusual activity.

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-10-13
Original CVE updated
2026-10-13
Advisory published
2026-10-13
Advisory updated
2026-10-13

Who should care

System administrators and security teams responsible for Windows systems should assess exposure and apply patches. Review system configurations to ensure least privilege access and monitor systems for unusual activity.

Why it matters

CVE-2026-70303 is a high-severity elevation of privilege vulnerability in the Windows Kernel. Defenders should prioritize patching affected systems, review configurations for least privilege access, and monitor for unusual activity. Evidence is based on official CVE and NVD records, and a Microsoft vendor advisory.

  • Elevation of privilege for attackers
  • Potential for lateral movement
  • Need for patch verification and system integrity checks
  • Possible impact on system availability and data confidentiality

Technical summary

The vulnerability exists due to an out-of-bounds write in the Windows Kernel. An authorized attacker can exploit this to elevate privileges locally. Affected versions include Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2, Windows 10 Version 22H2, Windows 11 version 23H2, Windows 11 Version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1, Windows 11 Version 26H2, Windows Server 2012, Windows Server 2012 (Server Core installation), Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation), Windows Server 2016, Windows Server 2016 (Server Core installation), Windows Server 2019, Windows Server 2019 (Server Core installation), Windows Server 2022, and Windows Server 2025.

Defensive priority

Apply patches immediately for Windows versions and editions listed as affected. Review system configurations and ensure that only necessary privileges are granted to users and services.

Recommended defensive actions

  • Apply patches for affected Windows versions and editions.
  • Review system configurations to ensure least privilege access.
  • Monitor systems for unusual activity.
  • Verify patch application and system integrity.

Evidence notes

The CVE Program and NVD provide official records of the vulnerability. Microsoft provides a vendor advisory with patch information. Evidence is based on official CVE and NVD records, and a Microsoft vendor advisory. The vulnerability affects multiple Windows versions and editions, including Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 21H2, Windows 10 Version 22H2, Windows 11 version 23H2, Windows 11 Version 23H2, Windows 11 Version 24H2, Windows 11 Version 25H2

Sources and references

Verified primary and authoritative sources

  • CVE-2026-70303 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-70303

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

  • CVE-2026-70303 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-70303

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

Supplemental references

  • Windows Kernel Elevation of Privilege Vulnerability

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/70xxx/CVE-2026-70303.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70303

    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.