CVE-2026-66799CriticalMicrosoft CVSS 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Microsoft security update for CVE-2026-66799 — Windows

Published
August 14, 2026
Last Modified
—

🔗 CVE IDs covered (1)

CVE-2026-66799 →

📋 Microsoft's advisory

EchelonGraph does not copy Microsoft's advisory page: its FAQ and remediation text are not shown here. Read the advisory on https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66799. This page also shows what EchelonGraph holds for CVE-2026-66799, with the description from its CVE record, which the CVE Numbering Authority that assigned the CVE wrote: for a CVE Microsoft assigned, often in the words of Microsoft's own advisory.

🎯 Affected products30

  • Windows 10 Version 1607 for 32-bit Systems
  • Windows 10 Version 1607 for x64-based Systems
  • Windows 10 Version 1809 for 32-bit Systems
  • Windows 10 Version 1809 for x64-based Systems
  • Windows 10 Version 21H2 for 32-bit Systems
  • Windows 10 Version 21H2 for ARM64-based Systems
  • Windows 10 Version 21H2 for x64-based Systems
  • Windows 10 Version 22H2 for 32-bit Systems
  • Windows 10 Version 22H2 for ARM64-based Systems
  • Windows 10 Version 22H2 for x64-based Systems
  • Windows 11 Version 23H2 for ARM64-based Systems
  • Windows 11 Version 23H2 for x64-based Systems
  • Windows 11 Version 24H2 for ARM64-based Systems
  • Windows 11 Version 24H2 for x64-based Systems
  • Windows 11 Version 25H2 for ARM64-based Systems
  • Windows 11 Version 25H2 for x64-based Systems
  • Windows 11 Version 26H1 for ARM64-based Systems
  • Windows 11 version 26H1 for x64-based Systems
  • 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
  • Windows Server 2022 (Server Core installation)
  • Windows Server 2025
  • Windows Server 2025 (Server Core installation)

✅ Updates Microsoft lists: 14 KB articles

17 rows: one per KB article or update, update type and fixed build. Their details are on Microsoft's advisory.

KB articleUpdateFixed build
KB5120238Security Update10.0.17763.9121
KB5120242Security Update10.0.20348.5499
KB5120229Security Hotpatch Update10.0.20348.5440
KB5123303Security Update10.0.20348.5499
KB5120249Security Update10.0.19044.7663
KB5120249Security Update10.0.19045.7663
KB5120233Security Update10.0.26100.33296
KB5120228Security Hotpatch Update10.0.26100.33222
KB5121003Security Update10.0.26200.9168
KB5120994Security Hotpatch Update10.0.26200.9106
KB5120240Security Update10.0.22631.7517
KB5121003Security Update10.0.26100.9168
KB5120994Security Hotpatch Update10.0.26100.9106
KB5121000Security Update10.0.28000.2704
KB5120418Security Update10.0.14393.9418
KB5120386Monthly Rollup6.2.9200.26280
KB5120385Monthly Rollup6.3.9600.23338

🧭 EchelonGraph on CVE-2026-66799

EchelonGraph score
7.8 HIGH
CISA KEV
Not listed
Fix status
A fix is available — apply it.

Description from the CVE record (CVE.org), as published by its numbering authority

Heap-based buffer overflow in Windows Key Guard allows an authorized attacker to elevate privileges locally.

Published by Microsoft Corporation, the CVE Numbering Authority that assigned CVE-2026-66799, in its CVE record at CVE.org; reused under the CVE Program's Terms of Use (its licence and MITRE's copyright notice are in our Terms of Service).

🔗 References (29)