dbcve.org
Windows 10 1809Operating system · Microsoft

CVE-2026-20857

HIGH · 7.8 CVSS v3.1 Published 2026-01-13
Fix available
A fix is available. Upgrade to 10.0.17763.8276 / 10.0.19044.6809 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
Untrusted pointer dereference 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

The vulnerability is an untrusted pointer dereference in the Windows Cloud Files Mini Filter Driver. This type of flaw occurs when the driver dereferences a pointer without properly validating its integrity or trustworthiness, allowing a local authenticated attacker to manipulate memory and elevate privileges to SYSTEM level.

MitigationApply the Microsoft security update for CVE-2026-20857 through Windows Update or WSUS. Prioritize patching systems with direct user access as the attacker requires local 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 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 11 24h2Operating system
Affected:< 10.0.26100.7623
Windows 11 25h2Operating system
Affected:< 10.0.26200.7623
Windows Server 2019Operating system
Affected:< 10.0.17763.8276
Windows Server 2022Operating system
Affected:< 10.0.20348.4648

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. Locate the Cloud Files Mini Filter Driver file
    Open PowerShell and run: Get-ChildItem -Path C:\Windows\System32\drivers -Filter cloudfilt.sys -ErrorAction SilentlyContinue | Select-Object FullName, Length, LastWriteTime
    Affected if The file cloudfilt.sys does not exist on the system (the driver may not be installed)
  2. Retrieve the driver file version
    Run in PowerShell: (Get-Item 'C:\Windows\System32\drivers\cloudfilt.sys').VersionInfo | Select-Object FileVersion, ProductVersion, FileDescription
    Affected if The version returned is lower than the version specified in the affected ranges for your Windows version
  3. Identify the installed Windows version
    Run in PowerShell: winver or [System.Environment]::OSVersion.Version and match against the Windows release (1809, 21h2, 22h2, 23h2, 24h2, 25h2, Server 2019, Server 2022)
    Affected if The Windows version and build number fall within the affected ranges listed in the CVE
  4. Check if the driver is loaded in memory
    Run in PowerShell: Get-Process | Where-Object {$_.Modules.ModuleName -eq 'cloudfilt.sys'} or use: driverquery /v | findstr cloudfilt
    Affected if The driver is actively loaded while the file version is below the fixed version for the detected Windows release

A system is affected if it runs any of the listed Windows versions with cloudfilt.sys present and its version is below the fixed version for that 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 10.0.17763.8276 / 10.0.19044.6809 / 10.0.19045.6809 or later
Fixed in 10.0.17763.827610.0.19044.680910.0.19045.6809
Interim mitigation

Apply the Microsoft security update for CVE-2026-20857 through Windows Update or WSUS. Prioritize patching systems with direct user access as the attacker requires local access.

Recommended fix High confidence

Microsoft security updates - patch to the minimum fixed build version for your Windows version (e.g., Windows 10 1809: KB[XXXXXXX] building to 10.0.17763.8276 or higher)

  1. Check current Windows version by running 'winver' or 'systeminfo' in Command Prompt
  2. Open Settings > Windows Update > Check for updates, or manually download the security update from the Microsoft Update Catalog (catalog.update.microsoft.com)
  3. Install the relevant security update for Windows Cloud Files Mini Filter Driver (CVE-2026-20857)
  4. Restart the computer when prompted to complete the installation
  5. Verify the update was installed successfully by checking 'View update history' in Windows Update
Caveat Standard Windows security update - no expected breaking changes; may require system restart

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

Fix this in Windows 10 1809 Scoped from the published advisory
  • Consultation8.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,940
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,304.

Scan for this in your stack

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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-2026-20857 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