dbcve.org
Windows 10 1607Operating system · Microsoft

CVE-2026-20940

HIGH · 7.8 CVSS v3.1 Published 2026-01-13
Fix available
A fix is available. Upgrade to 10.0.14393.8783 / 10.0.17763.8276 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 Cloud Files Mini Filter Driver allows an authorized attacker to elevate privileges locally.

In the news

Third-party coverage
Trending covered by 1 outlet this week · latest 7mo ago

Surfaced from public web coverage — external links open in a new tab.

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 vulnerability in Windows Cloud Files Mini Filter Driver enables a locally authorized attacker to elevate privileges to higher levels.

MitigationApply Microsoft security updates for the Cloud Files Mini Filter Driver when released; follow least-privilege principles and restrict local attacker access.

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:< 10.0.14393.8783
Windows 10 1809Operating system
Affected:< 10.0.17763.8276
Windows 10 21h2Operating system
Affected:< 10.0.19044.6809
Windows 10 22h2Operating system
Affected:< 10.0.19045.6809
Windows 11 23h2Operating system
Affected:< 10.0.22631.6491
Windows Server 2008Operating system
Affected:all versions= r2
Windows Server 2012Operating system
Affected:all versions= r2
Windows Server 2016Operating system
Affected:< 10.0.14393.8783

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. Check your Windows version
    Run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to identify your Windows build number
    Affected if Your version falls below 10.0.14393.8783 (Windows 10 1607/Server 2016), 10.0.17763.8276 (Windows 10 1809), 10.0.19044.6809 (Windows 10 21h2/22h2), or 10.0.22631.6491 (Windows 11 23h2), or is Windows Server 2008/2012 (all versions)
  2. Identify the Cloud Files Mini Filter Driver
    Open Services (services.msc) and look for a service related to Cloud Files Mini Filter, or run 'sc queryex type= service state= all' and search for 'Cloud Files' or 'cf' driver entries
    Affected if A Cloud Files Mini Filter Driver service exists and is running on your system
  3. Verify driver file version
    Locate the Cloud Files Mini Filter Driver file (typically in C:\Windows\System32\Drivers\) and right-click > Properties > Details to view the File Version, or use 'driverquery /v | findstr /i cloud'
    Affected if The driver file version is present and lower than the patched version for your Windows build
  4. Confirm driver is loaded
    Run 'fltmc filters' to list loaded filter drivers, or check 'HKLM\SYSTEM\CurrentControlSet\Services\CloudFiles' registry key for Start value (3 or less means driver loads at boot)
    Affected if The Cloud Files Mini Filter Driver is listed as an active filter driver

You are affected if your Windows version matches the affected ranges AND the Cloud Files Mini Filter Driver is present and enabled on your system.

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 10.0.14393.8783 / 10.0.17763.8276 / 10.0.19044.6809 or later
Fixed in 10.0.14393.878310.0.17763.827610.0.19044.6809
Interim mitigation

Apply Microsoft security updates for the Cloud Files Mini Filter Driver when released; follow least-privilege principles and restrict local attacker access.

Recommended fix High confidence

Windows 10 1607: 10.0.14393.8783 | Windows 10 1809: 10.0.17763.8276 | Windows 10 21h2: 10.0.19044.6809 | Windows 10 22h2: 10.0.19045.6809 | Windows 11 23h2: 10.0.22631.6491 | Windows Server 2016: 10.0.14393.8783

  1. Open Settings > Update & Security > Windows Update and check for updates
  2. Alternatively, open Command Prompt and run: 'winver' to check current version
  3. Apply the appropriate Windows Update patch for your version
  4. For Windows 10 1607: Update to build 10.0.14393.8783 or later
  5. For Windows 10 1809: Update to build 10.0.17763.8276 or later
  6. For Windows 10 21h2: Update to build 10.0.19044.6809 or later
  7. For Windows 10 22h2: Update to build 10.0.19045.6809 or later
  8. For Windows 11 23h2: Update to build 10.0.22631.6491 or later
Caveat Windows Server 2008 and 2012 are end-of-life with no security patches; upgrade to newer Windows Server versions

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
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,900
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,040.

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-2026-20940 in production — separate from our analysis above.

No notes yet

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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