# CVE-2021-33742: Microsoft Windows MSHTML Platform Remote Code Execution Vulnerability

Source: https://junglewise.ai/threats/cve-2021-33742-microsoft-windows-mshtml-platform-remote-code-execution  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-11-03. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2021-33742 · Severity: critical · CVSS 8.8 · Exploited in the wild · Published 2021-11-03

Microsoft Windows MSHTML Platform contains an out-of-bounds write vulnerability (CWE-787) that allows for remote code execution. The vulnerability is triggered when a user visits a specially crafted website or opens a malicious file, leading to memory corruption.

Technologies: [Microsoft Windows](https://junglewise.ai/threats/technologies/windows). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2021-33742 exploited in the wild?** Yes. CVE-2021-33742 is known to be exploited in the wild, first recorded on 3 November 2021. Treat it as urgent.

**How severe is CVE-2021-33742?** Critical severity, with a CVSS score of 8.8, published 3 November 2021.

**Which products and versions are affected?** Microsoft Windows 10 1507, 1607, 1809, 1909, 2004, 20H2, 21H1; Microsoft Windows 7 SP1; Microsoft Windows 8.1; Microsoft Windows RT 8.1; and 4 more.

**Is there a fix for CVE-2021-33742?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2021-33742 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2021-33742?** Check whether you run Microsoft Windows. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Microsoft Windows 10 1507, 1607, 1809, 1909, 2004, 20H2, 21H1
- Microsoft Windows 7 SP1
- Microsoft Windows 8.1
- Microsoft Windows RT 8.1
- Microsoft Windows Server 2008 R2 SP1, SP2
- Microsoft Windows Server 2012 R2
- Microsoft Windows Server 2016 2004, 20H2, 1909
- Microsoft Windows Server 2019

## Timeline

- 2021-06-14: disclosed: Initial analysis by NIST
- 2021-11-03: kev added: Added to CISA Known Exploited Vulnerabilities Catalog
- 2021-11-03: advisory: Published date listed in advisory
- 2021-11-03: exploited: Reported as exploited in the wild in CISA KEV catalog

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