---
id: "CVE-2021-40450"
kind: "vulnerability"
aliases: ["CVE-2021-40450"]
title: "Microsoft Win32k: Microsoft Win32k Privilege Escalation Vulnerability"
severity: "high"
cvss: 7.8
epss: 0.01582
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Microsoft Win32k", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exploited", "infrastructure", "self-hosted", "windows"]
not_affected_if: ["fully-patched-windows"]
published_at: "2021-10-13T01:15:09+00:00"
first_seen_at: "2026-10-23T19:11:52+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-2021-40450", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-40450", "first_seen_at": "2026-10-23T19:13:45+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-40450", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Microsoft Win32k: Microsoft Win32k Privilege Escalation Vulnerability

Microsoft Win32k, the Windows kernel-mode graphics subsystem, contains a flaw that lets a local user escalate privileges. Attackers exploit it in the wild, so a low-privilege foothold can become full control of the Windows machine.

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

## Affected

- vendor:Microsoft Win32k affected ? fixed ?

## Fix

Apply the Microsoft security update for CVE-2021-40450 per vendor instructions (CISA required action); the specific patched build is unknown from the sources.

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-40450
- 2026-10-23T19:13:45+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2021-40450
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-40450

## From the sources

Microsoft Win32k contains an unspecified vulnerability that allows for privilege escalation.

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_