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Windows 10 1607Operating system · Microsoft

CVE-2026-21248

HIGH · 7.3 CVSS v3.1 Published 2026-02-10
Fix available
A fix is available. Upgrade to 10.0.14393.8868 / 10.0.17763.8389 or later.
See remediation →
73/100
Remediation priority · Elevated

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Heap-based buffer overflow in Windows Hyper-V allows an authorized attacker to execute code locally.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Heap-based buffer overflow in Windows Hyper-V allows an authenticated attacker with local access to execute arbitrary code. The vulnerability involves improper memory bounds checking in Hyper-V's virtual machine management components, potentially allowing heap memory corruption and code execution within the hypervisor context.

MitigationApply Microsoft security updates for CVE-2026-21248 to all affected Windows Hyper-V host systems and validate virtual machine functionality after patching.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Windows 10 1607Operating system
Affected:< 10.0.14393.8868
Windows 10 1809Operating system
Affected:< 10.0.17763.8389
Windows 10 21h2Operating system
Affected:< 10.0.19044.6937
Windows 10 22h2Operating system
Affected:< 10.0.19045.6937
Windows 11 23h2Operating system
Affected:< 10.0.22631.6649
Windows 11 24h2Operating system
Affected:< 10.0.26100.7781
Windows 11 25h2Operating system
Affected:< 10.0.26200.7781
Windows Server 2016Operating system
Affected:< 10.0.14393.8868

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify Hyper-V is installed
    Run 'Get-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V' in PowerShell, or check 'systeminfo' for Hyper-V details
    Affected if Hyper-V is enabled and the system is acting as a Hyper-V host
  2. Confirm the host operating system version
    Run 'winver' or execute 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to identify the exact Windows release and build
    Affected if The Windows version matches any of the affected products listed (Windows 10 1607, 1809, 21h2, 22h2; Windows 11 23h2, 24h2, 25h2; or Windows Server 2016)
  3. Check the installed build number
    Run 'systeminfo' and locate the 'Build Number' field, or use 'reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion" /v CurrentBuild'
    Affected if The build number is lower than the fixed version for that Windows release (e.g., below 14393.8868 for Win10 1607/Server2016, below 17763.8389 for Win10 1809, below 19044.6937 for Win10 21h2, below 19045.6937 for Win10 22h2, below 22631.6649 for Win11 23h2, below 26100.7781 for Win11 24h2, below 2620
  4. Verify Hyper-V services are running
    Run 'Get-Service vmcompute, vmms, hvhost' in PowerShell to check if core Hyper-V services are active
    Affected if Any of these services are running on a system meeting the version criteria above

A system is affected if it runs Hyper-V and has a Windows build number lower than the fixed version for its specific Windows release.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 10.0.14393.8868 / 10.0.17763.8389 / 10.0.19044.6937 or later
Fixed in 10.0.14393.886810.0.17763.838910.0.19044.6937
Interim mitigation

Apply Microsoft security updates for CVE-2026-21248 to all affected Windows Hyper-V host systems and validate virtual machine functionality after patching.

Recommended fix High confidence

Apply the appropriate Windows security update for your version - fixed builds are: Windows 10 1607/Server 2016: 10.0.14393.8868 | Windows 10 1809: 10.0.17763.8389 | Windows 10 21h2: 10.0.19044.6937 | Windows 10 22h2: 10.0.19045.6937 | Windows 11 23h2: 10.0.22631.6649 | Windows 11 24h2: 10.0.26100.77

  1. Identify the current Windows version and build number by running `winver` or `systeminfo`
  2. Open Settings > Update & Security > Windows Update
  3. Click 'Check for updates' to download and install the latest cumulative security update
  4. Restart the system when prompted to complete the installation
  5. Verify the update was applied by checking the installed updates list or running `winver` to confirm the build number matches or exceeds the fixed version for your Windows edition
Caveat Standard Windows cumulative update apply with no special considerations beyond routine restart

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Windows 10 1607 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-21248 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data