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CVE record · CVE-2021-33742

Windows MSHTML Platform Remote Code Execution Vulnerability

CVSS 7.5 HighCriticalIn CISA KEVEPSS 0.59 · 99th percentile

Critical, because:

  • In CISA’s KEV catalogue since 3 Nov 2021: it is known to be exploited.
  • CVSS score 7.5 (7.0 or more) and EPSS 0.59 (0.1 or more): a high score and a real chance of exploitation in the next 30 days.

How we decide what’s critical

Published by the CVE Program (CNA: microsoft) at 8 Jun 2021, 22:46 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
VendorProductVersions
Microsoft Windows 10 Version 1809
  • affected 10.0.0 to before 10.0.17763.1999 custom
Microsoft Windows Server 2019
  • affected 10.0.0 to before 10.0.17763.1999 custom
Microsoft Windows 10 Version 1909
  • affected 10.0.0 to before 10.0.18363.1621 custom
Microsoft Windows 10 Version 21H1
  • affected 10.0.0 to before 10.0.19043.1052 custom
Microsoft Windows 10 Version 2004
  • affected 10.0.0 to before 10.0.19041.1052 custom
Microsoft Windows 10 Version 20H2
  • affected 10.0.0 to before 10.0.19042.1052 custom
Microsoft Windows 10 Version 1507
  • affected 10.0.0 to before 10.0.10240.18967 custom
Microsoft Windows 10 Version 1607
  • affected 10.0.0 to before 10.0.14393.4467 custom
Microsoft Windows Server 2016
  • affected 10.0.0 to before 10.0.14393.4467 custom
Microsoft Windows 7
  • affected 6.1.0 to before 6.1.7601.25632 custom
  • affected 6.1.0 to before publication custom
Microsoft Windows 7 Service Pack 1
  • affected 6.1.0 to before 6.1.7601.25632 custom
  • affected 6.1.0 to before publication custom
Microsoft Windows 8.1
  • affected 6.3.0 to before 6.3.9600.20045 custom
  • affected 6.3.0 to before 1.0.0.0 custom
Microsoft Windows Server 2008 Service Pack 2
  • affected 6.0.0 to before 6.0.6003.21137 custom
  • affected 6.0.0 to before publication custom
Microsoft Windows Server 2008 Service Pack 2
  • affected 6.0.0 to before 6.0.6003.21137 custom
  • affected 6.0.0 to before publication custom
Microsoft Windows Server 2008 R2 Service Pack 1
  • affected 6.1.0 to before 6.1.7601.25632 custom
  • affected 6.1.0 to before publication custom
Microsoft Windows Server 2012
  • affected 6.2.0 to before 6.2.9200.23372 custom
  • affected 6.2.0 to before 1.0.0.0 custom
Microsoft Windows Server 2012 R2
  • affected 6.3.0 to before 6.3.9600.20045 custom
  • affected 6.3.0 to before 1.0.0.0 custom
Identifiers
CVE-2021-33742
CNA
microsoft
Weakness (CWE)
CWE-787
Tags
Published
8 Jun 2021
Updated
21 Oct 2025

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.5 High 3.1 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 CNA (microsoft)
  • CISA KEV Listed since 3 Nov 2021: known to be exploited.
  • EPSS 0.59, the 99th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 8 Jun 2021. New records show when each source confirmed them.

Sources

References from the CNA

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.