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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 1803Operating system · Microsoft

CVE-2021-28310

HIGH · 7.8 CVSS v3.1 Developing Published 2021-04-13
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
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
Win32k 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 · low confidence

CVE-2021-28310 is an elevation of privilege vulnerability in the Windows Win32k kernel-mode driver (win32k.sys). This flaw allows a local authenticated attacker to gain SYSTEM privileges by exploiting improper handling of objects in kernel mode.

MitigationApply the Microsoft security updates released in April 2021. Prior to patching, monitor for indicators of compromise and restrict user privileges to minimize attack surface.

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 1803Operating system
Affected:all versions
Windows 10 1809Operating system
Affected:all versions
Windows 10 1909Operating system
Affected:all versions
Windows 10 2004Operating system
Affected:all versions
Windows 10 20h2Operating system
Affected:all versions
Windows Server 1909Operating system
Affected:all versions
Windows Server 2004Operating system
Affected:all versions
Windows Server 2019Operating 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. Identify Windows version
    Run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to get the Windows version and build number
    Affected if The version matches any of the affected products: Windows 10 1803, 1809, 1909, 2004, 20H2, or Windows Server 1909, 2004, 2019
  2. Confirm build number
    Run 'winver' or check System Properties to verify the exact build number (for example, 10.0.18362, 10.0.19041, etc.)
    Affected if The build number falls within the range for any affected Windows 10 or Windows Server version listed in the CVE
  3. Check for April 2021 security updates
    Open Control Panel > Programs and Features > View installed updates, or run 'wmic qfe list' to list installed hotfixes. Look for security updates released in April 2021
    Affected if No April 2021 security updates are installed, indicating the system may be missing the patch for this vulnerability
  4. Verify win32k.sys version
    Navigate to C:\Windows\System32\drivers\win32k.sys, right-click > Properties > Details to view file version and product version
    Affected if The file version is older than the patched version released in April 2021, or the product version does not match the patched build for your Windows version

The system is likely affected if it runs any of the listed Windows 10 or Windows Server versions AND lacks the April 2021 security updates.

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
Patch available Apply the vendor patch
Vendor patch portal.msrc.microsoft.com →
Interim mitigation

Apply the Microsoft security updates released in April 2021. Prior to patching, monitor for indicators of compromise and restrict user privileges to minimize attack surface.

Recommended fix High confidence

Install the March 2021 Windows security update (KB5000802 for Windows 10 2004/20h2, KB5000822 for Windows 10 1909, KB5000842 for Windows 10 1809, or the equivalent update for your specific version)

  1. Open Windows Update settings (Settings > Update & Security > Windows Update)
  2. Click 'Check for updates' to download and install the latest security updates
  3. Alternatively, manually download and install the specific security update for this vulnerability from the Microsoft Update Catalog
  4. Restart the system after installing the update
  5. Verify the update was installed successfully by checking the installed updates list
Caveat None - this is a routine security patch with no expected compatibility issues

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

Fix this in Windows 10 1803 Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-28310 — 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-2021-28310 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