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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 17 Nov 2021.
Windows 10 1507Operating system · Microsoft

CVE-2021-31956

HIGH · 7.8 CVSS v3.1 Published 2021-06-08
Fix available
A fix is available. Upgrade to 10.0.10240.18967 / 10.0.14393.4467 or later.
See remediation →
96/100
Remediation priority · Urgent
In the wild Zero-click Patch available

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 NTFS Elevation of Privilege 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

CVE-2021-31956 is a Windows NTFS elevation of privilege vulnerability with a CVSS 7.8 (HIGH). It allows a local attacker to exploit a flaw in NTFS file system handling to escalate privileges, likely by tricking the system into improper file operations or permission handling.

MitigationApply the Microsoft security update for CVE-2021-31956 via Windows Update or the relevant patch from Microsoft's June 2021 security bulletin.

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 1507Operating system
Affected:< 10.0.10240.18967
Windows 10 1607Operating system
Affected:< 10.0.14393.4467
Windows 10 1809Operating system
Affected:< 10.0.17763.1999
Windows 10 1909Operating system
Affected:< 10.0.18363.1621
Windows 10 2004Operating system
Affected:< 10.0.19041.1052
Windows 10 20h2Operating system
Affected:< 10.0.19042.1052
Windows 10 21h1Operating system
Affected:< 10.0.19043.1052
Windows 7Operating system
Affected:all versions

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 Windows 10 build version
    Run 'winver' from command prompt or check 'systeminfo | findstr /B /C:"OS Version"' to obtain the full build number (e.g., 10.0.19041.1052)
    Affected if The build number is less than the threshold for your Windows 10 release channel (1507: <18967, 1607: <4467, 1809: <1999, 1909: <1621, 2004: <1052, 20h2: <1052, 21h1: <1052)
  2. Check Windows 7 version
    Run 'winver' or check 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"'
    Affected if The system runs any version of Windows 7 (all versions are affected)
  3. Verify patch installation status
    Run 'wmic qfe get HotFixID,InstalledOn' or check Windows Update history for the June 2021 security updates (KB5003635 or later cumulative update)
    Affected if The June 2021 security updates are not installed and the Windows version falls within the affected unpatched ranges

The system is affected if it runs Windows 7 (any version) or Windows 10 with a build number below the fixed threshold for its release and the June 2021 security updates have not been applied.

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 10.0.10240.18967 / 10.0.14393.4467 / 10.0.17763.1999 or later
Fixed in 10.0.10240.1896710.0.14393.446710.0.17763.1999
Vendor patch portal.msrc.microsoft.com →
Interim mitigation

Apply the Microsoft security update for CVE-2021-31956 via Windows Update or the relevant patch from Microsoft's June 2021 security bulletin.

Recommended fix High confidence

Windows 10 21h1 (build 19043.1052) or later; for Windows 7 systems migrate to Windows 10/11

  1. Check the current Windows version by running 'winver' in the Run dialog or 'systeminfo' in Command Prompt
  2. Determine which Windows 10 build is currently installed and compare against the vulnerable versions listed (1507, 1607, 1809, 1909, 2004, 20h2, 21h1)
  3. For Windows 10 systems: Navigate to Settings > Update & Security > Windows Update and check for updates to receive the security patch containing the fix
  4. For Windows 7 systems: Since Windows 7 is end-of-life with no security updates, migrate to a supported Windows version (Windows 10 or Windows 11)
  5. Verify the fix by checking that the build number meets or exceeds: 10.0.10240.18967 (1507), 10.0.14393.4467 (1607), 10.0.17763.1999 (1809), 10.0.18363.1621 (1909), 10.0.19041.1052 (2004), 10.0.19042.1052 (20h2), or 10.0.19043.1052 (21h1)
Caveat Ensure application and driver compatibility before upgrading; Windows 7 end-of-life means no direct patch path - full OS migration required

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

Fix this in Windows 10 1507 Exploited in the wild — priority engagement
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-31956 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-31956 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