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CVE-2021-33742

Windows MSHTML Platform Remote Code Execution Vulnerability

  • High 7.5
  • Exploited: added to CISA KEV 3 Nov 2021

Description

Windows MSHTML Platform Remote Code Execution Vulnerability

Key facts

Published
8 Jun 2021
Last changed
21 Oct 2025
Assigned by
microsoft
KEV added
3 Nov 2021
KEV fix due
17 Nov 2021
EPSS
59.407% likely to be exploited in the next 30 days, higher than 99.137% of CVEs (scores for 15 Nov 2026)
SSVC (CISA)
Exploitation: active; Automatable: no; Technical impact: total

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

  • 7.5CVSS 3.1, Highfrom the CNA (microsoft)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

What to do

  • Apply updates per vendor instructions.CISA KEV required action

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

VendorProductVersions
MicrosoftWindows 10 Version 1809
  • 10.0.0 up to but excluding 10.0.17763.1999 (affected)
MicrosoftWindows Server 2019
  • 10.0.0 up to but excluding 10.0.17763.1999 (affected)
MicrosoftWindows 10 Version 1909
  • 10.0.0 up to but excluding 10.0.18363.1621 (affected)
MicrosoftWindows 10 Version 21H1
  • 10.0.0 up to but excluding 10.0.19043.1052 (affected)
MicrosoftWindows 10 Version 2004
  • 10.0.0 up to but excluding 10.0.19041.1052 (affected)
MicrosoftWindows 10 Version 20H2
  • 10.0.0 up to but excluding 10.0.19042.1052 (affected)
MicrosoftWindows 10 Version 1507
  • 10.0.0 up to but excluding 10.0.10240.18967 (affected)
MicrosoftWindows 10 Version 1607
  • 10.0.0 up to but excluding 10.0.14393.4467 (affected)
MicrosoftWindows Server 2016
  • 10.0.0 up to but excluding 10.0.14393.4467 (affected)
MicrosoftWindows 7
  • 6.1.0 up to but excluding 6.1.7601.25632 (affected)
  • 6.1.0 up to but excluding publication (affected)
MicrosoftWindows 7 Service Pack 1
  • 6.1.0 up to but excluding 6.1.7601.25632 (affected)
  • 6.1.0 up to but excluding publication (affected)
MicrosoftWindows 8.1
  • 6.3.0 up to but excluding 6.3.9600.20045 (affected)
  • 6.3.0 up to but excluding 1.0.0.0 (affected)
MicrosoftWindows Server 2008 Service Pack 2
  • 6.0.0 up to but excluding 6.0.6003.21137 (affected)
  • 6.0.0 up to but excluding publication (affected)
MicrosoftWindows Server 2008 Service Pack 2
  • 6.0.0 up to but excluding 6.0.6003.21137 (affected)
  • 6.0.0 up to but excluding publication (affected)
MicrosoftWindows Server 2008 R2 Service Pack 1
  • 6.1.0 up to but excluding 6.1.7601.25632 (affected)
  • 6.1.0 up to but excluding publication (affected)
MicrosoftWindows Server 2012
  • 6.2.0 up to but excluding 6.2.9200.23372 (affected)
  • 6.2.0 up to but excluding 1.0.0.0 (affected)
MicrosoftWindows Server 2012 R2
  • 6.3.0 up to but excluding 6.3.9600.20045 (affected)
  • 6.3.0 up to but excluding 1.0.0.0 (affected)

Timeline

  1. 8 Jun 2021 Published
  2. 3 Nov 2021 CVE-2021-33742 added to CISA KEV
  3. 3 Nov 2021 Added to the CISA KEV catalogue

Weakness

References