Is CVE-2021-33739 being actively exploited?

Yes. CVE-2021-33739 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added on November 3, 2021.

What is the CVSS score for CVE-2021-33739?

CVE-2021-33739 has a CVSS 3.1 base score of 8.4 (HIGH).

CVE-2021-33739

HIGH · CVSS 8.4CISA KEV: actively exploitedEPSS 6.6%EU EUVD: exploited

Microsoft DWM Core Library Elevation of Privilege Vulnerability

Key facts

CVSS score: 8.4 (v3.1)
Severity: HIGH
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS score: 6.6% (94th percentile)
In CISA KEV: Yes, added November 3, 2021
In EU EUVD: Yes (EUVD-2021-20416)
Published: June 8, 2021
NVD last modified: June 17, 2026
Status: Analyzed

CISA Known Exploited Vulnerability

Microsoft Desktop Window Manager (DWM) Core Library Privilege Escalation Vulnerability

Added to the KEV catalog on November 3, 2021; federal remediation due November 17, 2021.

EU Vulnerability Database (EUVD)

This vulnerability is also tracked by ENISA as EUVD-2021-20416 in the EU Vulnerability Database. ENISA flags it as known exploited. Last updated in EUVD on October 21, 2025.

View on the EU Vulnerability Database

Affected products

microsoft / windows 10 1909
microsoft / windows 10 2004
microsoft / windows 10 20h2
microsoft / windows 10 21h1
microsoft / windows server 2004
microsoft / windows server 20h2

Certified products that may be affected

2 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.

Microsoft Windows 10 version 2004 (May 2020 Update), Microsoft Windows Server version 2004 (May 2020 Update) and others - Microsoft Corporation - Common Criteria 2020-50-INF-3671 - active
Microsoft Windows 10 version 1909 and Microsoft Windows Server version 1909 - Microsoft Corporation - Common Criteria 2019-47-INF-3134 - archived

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33739(Patch, Vendor Advisory)
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-33739(US Government Resource)

Last updated September 17, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS

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