---
id: "CVE-2021-21220"
kind: "vulnerability"
aliases: ["CVE-2021-21220"]
title: "Google Chromium V8: Google Chromium V8 Improper Input Validation Vulnerability"
severity: "high"
cvss: 8.8
epss: 0.70435
exploited: true
status: "open"
category: "runtime"
products: [{"name": "Google Chromium V8", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["browsers", "chrome", "chromium", "edge", "exploited", "opera", "runtime"]
not_affected_if: ["fixed-browser-version"]
published_at: "2021-04-26T17:15:08+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-2021-21220", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-21220", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-21220", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Google Chromium V8: Google Chromium V8 Improper Input Validation Vulnerability

A flaw in the V8 JavaScript engine used by Chromium browsers lets a remote attacker corrupt heap memory with a crafted HTML page. Successful exploitation can lead to arbitrary code execution in the browser.

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

## Affected

- vendor:Google Chromium V8 affected ? fixed ?

## How to check

Open chrome://version (or edge://version, opera://about) and compare the version with the fixed release in the vendor advisory.

## Fix

Update Google Chrome, Microsoft Edge, Opera and other Chromium-based browsers to a release that includes the vendor's V8 fix.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-21220
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2021-21220
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-21220

## From the sources

Google Chromium V8 Engine contains an improper input validation vulnerability that allows a remote attacker to potentially exploit heap corruption via a crafted HTML page. This vulnerability could affect multiple web browsers that utilize Chromium, including, but not limited to, Google Chrome, Microsoft Edge, and Opera.

CISA required action: Apply updates per vendor instructions.

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