---
id: "CVE-2021-37973"
kind: "vulnerability"
aliases: ["CVE-2021-37973"]
title: "Google Chromium Portals: Google Chromium Portals Use-After-Free Vulnerability"
severity: "critical"
cvss: 9.6
epss: 0.11735
exploited: true
status: "open"
category: "runtime"
products: [{"name": "Google Chromium Portals", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["browser-users", "chrome", "chromium", "edge", "exploited", "runtime"]
not_affected_if: ["browser-already-patched"]
published_at: "2021-10-08T22:15:08+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-2021-37973", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-37973", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-37973", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Google Chromium Portals: Google Chromium Portals Use-After-Free Vulnerability

A use-after-free bug in Chromium's Portals feature lets a remote attacker who already controls the renderer process escape the browser sandbox via a crafted HTML page. CISA lists it as actively exploited in the wild.

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

## Affected

- vendor:Google Chromium Portals affected ? fixed ?

## How to check

Open chrome://version or edge://version and compare the version to the fixed release in the vendor advisory.

## Fix

Update Google Chrome and Microsoft Edge (or other Chromium-based browsers) to the latest stable release, per vendor instructions.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-37973
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2021-37973
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-37973

## From the sources

Google Chromium Portals contains a use-after-free vulnerability that allows a remote attacker, who has compromised the renderer process, to potentially perform a sandbox escape via a crafted HTML page. This vulnerability affects web browsers that utilize Chromium, including Google Chrome and Microsoft Edge.

CISA required action: Apply updates per vendor instructions.

---

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