How severe is CVE-2021-33742?

CVE-2021-33742 has a CVSS 3.1 base score of 7.5 (HIGH). EPSS estimates a 59.4% probability of exploitation in the next 30 days. It is listed in the CISA Known Exploited Vulnerabilities catalog.

CVE-2021-33742: Windows MSHTML Platform Remote Code Execution

CISA Known Exploited Vulnerabilities

Microsoft Windows MSHTML Platform Remote Code Execution Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.

Added to KEV

2021-11-03

Remediation due

2021-11-17

Required action
Apply updates per vendor instructions.

CISA notes
https://nvd.nist.gov/vuln/detail/CVE-2021-33742

Description

Windows MSHTML Platform Remote Code Execution Vulnerability

Severity

CVSS 3.1 · CNA7.5 HIGH

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C

SSVC · CISA-ADP

Exploitationactive

Automatableno

Technical impacttotal

Exploitation Context

as of October 17, 2026

All KEV statistics→

CISA added CVE-2021-33742 to the KEV catalog 148 days after its CVE record was published.
It is one of 391 Microsoft entries in the CISA KEV catalog, and one of 83 added in 2021.
Its current EPSS score (59.4%) is higher than that of 53% of CISA KEV entries.

Affected Products

Vendor	Product	Affected versions
Microsoft	Microsoft Windows 10 Version 1809	10.0.0 to <10.0.17763.1999
Microsoft	Microsoft Windows Server 2019	10.0.0 to <10.0.17763.1999
Microsoft	Microsoft Windows 10 Version 1909	10.0.0 to <10.0.18363.1621
Microsoft	Microsoft Windows 10 Version 21H1	10.0.0 to <10.0.19043.1052
Microsoft	Microsoft Windows 10 Version 2004	10.0.0 to <10.0.19041.1052
Microsoft	Microsoft Windows 10 Version 20H2	10.0.0 to <10.0.19042.1052
Microsoft	Microsoft Windows 10 Version 1507	10.0.0 to <10.0.10240.18967
Microsoft	Microsoft Windows 10 Version 1607	10.0.0 to <10.0.14393.4467
Microsoft	Microsoft Windows Server 2016	10.0.0 to <10.0.14393.4467
Microsoft	Microsoft Windows 7	6.1.0 to <6.1.7601.25632 6.1.0 to <publication
Microsoft	Microsoft Windows 7 Service Pack 1	6.1.0 to <6.1.7601.25632 6.1.0 to <publication
Microsoft	Microsoft Windows 8.1	6.3.0 to <6.3.9600.20045 6.3.0 to <1.0.0.0
Microsoft	Microsoft Windows Server 2008 Service Pack 2	6.0.0 to <6.0.6003.21137 6.0.0 to <publication
Microsoft	Microsoft Windows Server 2008 Service Pack 2	6.0.0 to <6.0.6003.21137 6.0.0 to <publication
Microsoft	Microsoft Windows Server 2008 R2 Service Pack 1	6.1.0 to <6.1.7601.25632 6.1.0 to <publication
Microsoft	Microsoft Windows Server 2012	6.2.0 to <6.2.9200.23372 6.2.0 to <1.0.0.0
Microsoft	Microsoft Windows Server 2012 R2	6.3.0 to <6.3.9600.20045 6.3.0 to <1.0.0.0

References

1 Links

Other references

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33742

Record Details

Published

2021-06-08

Last updated

2025-10-21

Assigner (CNA)

microsoft

Credited to

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CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.