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Windows 10Operating system · Microsoft

CVE-2021-1663

MEDIUM · 5.5 CVSS v3.1 Published 2021-01-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
57/100
Remediation priority · Elevated
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
Windows Projected File System FS Filter Driver Information Disclosure Vulnerability

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

This is an information disclosure vulnerability in the Windows Projected File System (ProjFS) FS Filter Driver. The vulnerability allows a local attacker to potentially access sensitive information due to improper handling of file system operations in the kernel-mode filter driver.

MitigationApply the relevant Windows security update (Microsoft released patches for this CVE in January 2021) to all affected Windows systems to remediate this vulnerability.

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 10Operating system
Affected:= 20h2= 2004
Windows Server 2016Operating system
Affected:= 20h2= 2004

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
None
Availability
None

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

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 Windows build number
    Run 'winver' from the Run dialog or execute 'systeminfo' in Command Prompt and look at the 'OS Version' line to identify if the build matches Windows 10 version 20h2 or version 2004, or Windows Server 2019 version 20h2
    Affected if The installed Windows build corresponds to version 2004 or version 20h2 for Windows 10 or Windows Server 2016
  2. Verify ProjFS filter driver status
    Open an elevated Command Prompt and run 'fltmc filters' to list all loaded minifilter drivers. Look for 'ProjFS' or 'mrxdav' in the output, as ProjFS may be loaded through the WebDAV redirector
    Affected if The ProjFS (Projected File System) minifilter driver is loaded and active on the system
  3. Confirm Windows product edition
    Run 'winver' or 'systeminfo' and verify the Windows edition is either Windows 10 or Windows Server 2016
    Affected if The system is running Windows 10 version 2004 or 20h2, or Windows Server 2016 version 20h2 or 2004

A system is affected if it runs Windows 10 version 2004 or 20h2 (or Windows Server 2016 matching those version numbers) AND has the ProjFS filter driver loaded or available on the 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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the relevant Windows security update (Microsoft released patches for this CVE in January 2021) to all affected Windows systems to remediate this vulnerability.

Fix this in Windows 10 Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $750
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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-2021-1663 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