CVE-2021-33739
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 · uneditedMicrosoft DWM Core Library 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 · high confidenceThis is an Elevation of Privilege vulnerability in the Microsoft DWM (Desktop Window Manager) Core Library (dwmcore.dll). An attacker could exploit this vulnerability to elevate privileges from a low-privileged user context to a higher privileged context, potentially achieving SYSTEM-level access on affected Windows systems.
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< 10.0.18363.1621< 10.0.19041.1052< 10.0.19042.1052< 10.0.19043.1052< 10.0.19041.1052< 10.0.19042.1052CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:N/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 checksWork through these to decide whether this CVE applies to you.
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Identify Windows version and build numberOpen Command Prompt and run 'winver' or check System Information (msinfo32.exe). Note the Windows version and the Build Number displayed.Affected if The build number is lower than 18363.1621 for Windows 10 1909, lower than 19041.1052 for Windows 10 2004 or Server 2004, lower than 19042.1052 for Windows 10 20H2 or Server 20H2, or lower than 19043.1052 for Windows 10 21H1.
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Verify DWM Core Library is presentCheck that dwmcore.dll exists at C:\Windows\System32\dwmcore.dll using File Explorer or the command 'dir C:\Windows\System32\dwmcore.dll'.Affected if The file exists and the system version matches the vulnerable build ranges listed above.
Your system is affected if it runs Windows 10 1909, 2004, 20H2, or 21H1 (or Windows Server 2004/20H2) with a build number below the corresponding threshold for that version.
Generated from the published advisory. Verify against your own configuration.
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 · scoped10.0.18363.162110.0.19041.105210.0.19042.1052
Apply the Microsoft security update for CVE-2021-33739 via Windows Update or deploy the applicable security patch through your organization's patch management process.
June 2021 Windows Security Update (KB5003635) - minimum fixed builds: 10.0.18363.1621 (1909), 10.0.19041.1052 (2004), 10.0.19042.1052 (20H2), 10.0.19043.1052 (21H1)
- Open Windows Update settings on the affected Windows 10 or Windows Server system
- Check for updates and install all available security updates
- Alternatively, manually install the June 2021 security updates (KB5003635 or subsequent updates) from Microsoft Update Catalog
- Restart the system after installing updates to apply the fixes
- Verify the installed updates by running 'winver' or checking System Information to confirm the build number matches or exceeds the fixed version for your Windows 10/Server release
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,848.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-33739 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-33739 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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