CVE-2021-33742
HighExploitedPublic exploitWindows MSHTML Platform Remote Code Execution Vulnerability
Published Jun 11, 2021 · Updated Oct 21, 2025
Key Facts
Patch immediately- CVE-2021-33742 is a high-severity vulnerability (CVSS 8.8 v3.1) affecting Windows 10 1507 (Microsoft), Windows 10 1607 (Microsoft), Windows 10 1809 (Microsoft) and 14 more products.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 3, 2021. Public exploit code is available.
- EPSS estimates a 59% probability of exploitation in the next 30 days.
- Fixed versions are available, including Windows 10 1507 10.0.10240.18967, Windows 10 1607 10.0.14393.4467, Windows 10 1809 10.0.17763.1999.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
8.8
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
59%
Higher than 99.1% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-33742 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
Windows MSHTML Platform Remote Code Execution Vulnerability
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Nov 3, 2021 | Nov 17, 2021 | Not reported |
| Industry KEV feed | Jun 3, 2021 | Nov 17, 2021 | Not reported |
| CIRCL KEV | Nov 3, 2021 | Nov 17, 2021 | Not reported |
| ENISA EUVD | Nov 3, 2021 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
53 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Windows 10 1507Microsoft | 10.0.10240.18967 | 10.0.10240.18967 |
| Windows 10 1607Microsoft | 10.0.14393.4467 | 10.0.14393.4467 |
| Windows 10 1809Microsoft | 10.0.17763.1999, 10.0.18363.1621, 10.0.19041.1052 | 10.0.17763.1999 |
| Windows 10 1909Microsoft | 10.0.18363.1621 | 10.0.18363.1621 |
| Windows 10 2004Microsoft | See advisory | 10.0.19041.1052 |
Patched Releases
Windows 10 1507
10.0.10240.18967
Windows 10 1607
10.0.14393.4467
Windows 10 1809
10.0.17763.1999, 10.0.18363.1621, 10.0.19041.1052
Windows 10 1909
10.0.18363.1621
Windows 10 2004
10.0.19041.1052
windows 10 20H2
10.0.19042.1052
windows 10 21H1
10.0.19043.1052
Windows 7
6.1.7601.25632, publication
Windows 8.1
1.0.0.0, 6.3.9600.20045
Windows Rt 8.1
1.0.0.0, 6.3.9600.20045
windows server 2008 R2
6.1.7601.25632, publication
Windows Server 2008 Sp2
6.0.6003.21137, publication
Windows Server 2012
1.0.0.0, 6.2.9200.23372
windows server 2012 R2
1.0.0.0, 6.3.9600.20045
Windows Server 2016
10.0.14393.4467
Windows Server 2019
10.0.17763.1999
Timeline
Added to Industry KEV feed
Jun 3, 2021
Publicly disclosed
Jun 11, 2021
Added to CISA KEV
Nov 3, 2021
Added to CIRCL KEV
Nov 3, 2021
Added to ENISA EUVD
Nov 3, 2021
Last updated
Oct 21, 2025
Weakness Type
- CWE-787 Out-of-bounds Write
References
- advisoryhttps://gbhackers.com/google-fixes-chrome-0-day-flaw/
- advisoryhttps://t.co/1RDbbuiBfY
- advisoryhttps://t.co/Ap9dEq98Cy
- advisoryhttps://us-cert.cisa.gov/ncas/current-activity/2021/06/10/google-releases-security-updates-chrome
- advisoryhttps://www.computing.co.uk/news/4032682/google-releases-urgent-chrome-update-address-zero-day-bug-active-attack
FAQ
Common Questions.
Windows MSHTML Platform Remote Code Execution Vulnerability
Affected: Windows 10 1507 (Microsoft) versions 10.0.10240.18967; Windows 10 1607 (Microsoft) versions 10.0.14393.4467; Windows 10 1809 (Microsoft) versions 10.0.17763.1999, 10.0.18363.1621, 10.0.19041.1052, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jun 3, 2021.
Yes. It was added on Nov 3, 2021 with a federal remediation due date of Nov 17, 2021.
Public exploit code is available.
Fixed versions are available, including Windows 10 1507 10.0.10240.18967, Windows 10 1607 10.0.14393.4467, Windows 10 1809 10.0.17763.1999.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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