---
id: "CVE-2021-33742"
kind: "vulnerability"
aliases: ["CVE-2021-33742"]
title: "Microsoft Windows: Microsoft Windows MSHTML Platform Remote Code Execution Vulnerability"
severity: "high"
cvss: 8.8
epss: 0.59407
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Microsoft Windows", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["desktop", "exploited", "infrastructure", "office", "windows"]
not_affected_if: ["patched-windows"]
published_at: "2021-06-08T23:15:09+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-33742", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-33742", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-33742", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Microsoft Windows: Microsoft Windows MSHTML Platform Remote Code Execution Vulnerability

Microsoft Windows MSHTML Platform, the browser engine component used by Windows, has a remote code execution flaw. Attackers are exploiting it in the wild, so a crafted file or page can run code on the affected machine.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Microsoft Windows affected ? fixed ?

## Fix

Apply the Microsoft security update for CVE-2021-33742 per vendor instructions, as CISA requires.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-33742
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2021-33742
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-33742

## From the sources

Microsoft Windows MSHTML Platform contains an unspecified vulnerability that allows for remote code execution.

CISA required action: Apply updates per vendor instructions.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_