dbcve.org
Windows 10 1607Operating system · Microsoft

CVE-2026-40398

HIGH · 7.8 CVSS v3.1 Published 2026-05-12
Fix available
A fix is available. Upgrade to 10.0.14393.9140 / 10.0.17763.8755 or later.
See remediation →
80/100
Remediation priority · High
Zero-click

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 Remote Desktop allows an authorized attacker to elevate privileges 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 Remote Desktop service allows a local authorized attacker to corrupt heap memory and elevate privileges to higher integrity levels. The vulnerability stems from improper bounds checking when handling Remote Desktop protocol operations.

MitigationApply Microsoft security updates for Windows Remote Desktop when released. Disable Remote Desktop if not required, and restrict local access to trusted users only.

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:< 10.0.14393.9140
Windows 10 1809Operating system
Affected:< 10.0.17763.8755
Windows 10 21h2Operating system
Affected:< 10.0.19044.7291
Windows 10 22h2Operating system
Affected:< 10.0.19045.7291
Windows 11 23h2Operating system
Affected:< 10.0.22631.7079
Windows 11 24h2Operating system
Affected:< 10.0.26100.8390
Windows 11 25h2Operating system
Affected:< 10.0.26200.8390
Windows 11 26h1Operating system
Affected:< 10.0.28000.2113

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
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/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. Identify Windows version and build number
    Open Command Prompt and run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to see the exact Windows version and build number
    Affected if The build number falls below the threshold for your Windows version (see version-specific thresholds in the CVE)
  2. Verify Remote Desktop service status
    Open Services (services.msc) and check if 'Remote Desktop Services' (TermService) is running, or run 'sc query TermService' in Command Prompt
    Affected if Remote Desktop service is enabled and running - the vulnerability exists in the RDP service itself
  3. Check RDP registry configuration
    Run 'reg query "HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server" /v fDenyTSConnections' in Command Prompt - a value of 0 means RDP is enabled
    Affected if The registry value shows RDP is enabled (fDenyTSConnections = 0)
  4. Compare installed version against affected ranges
    Match your Windows edition/version to the list: Windows 10 1607 needs build < 14393.9140, 1809 needs < 17763.8755, 21h2 needs < 19044.7291, 22h2 needs < 19045.7291, Windows 11 23h2 needs < 22631.7079, 24h2 needs < 26100.8390, 25h2 needs < 26200.8390, 26h1 needs < 28000.2113
    Affected if Your installed build number is lower than the threshold for your specific Windows version

You are affected if Remote Desktop is enabled AND your Windows build number is below the threshold for your Windows version.

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 10.0.14393.9140 / 10.0.17763.8755 / 10.0.19044.7291 or later
Fixed in 10.0.14393.914010.0.17763.875510.0.19044.7291
Interim mitigation

Apply Microsoft security updates for Windows Remote Desktop when released. Disable Remote Desktop if not required, and restrict local access to trusted users only.

Recommended fix High confidence

Windows 10 1607: 10.0.14393.9140 | Windows 10 1809: 10.0.17763.8755 | Windows 10 21h2: 10.0.19044.7291 | Windows 10 22h2: 10.0.19045.7291 | Windows 11 23h2: 10.0.22631.7079 | Windows 11 24h2: 10.0.26100.8390 | Windows 11 25h2: 10.0.26200.8390 | Windows 11 26h1: 10.0.28000.2113

  1. Identify the current Windows version and build number by running 'winver' or 'systeminfo' in Command Prompt
  2. Determine which Windows release version (1607, 1809, 21h2, 22h2, 23h2, 24h2, 25h2, or 26h1) matches your system
  3. Apply the appropriate Windows Update or manually install the security update corresponding to your release version
  4. Verify the installation was successful by checking the build number matches or exceeds the fixed version for your release
  5. Restart the system if prompted to complete the update installation
Caveat Standard Windows security update - minimal risk; ensure regular backups and compatibility testing for business-critical applications before deployment

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

Fix this in Windows 10 1607 Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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Scan for this in your stack

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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-2026-40398 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