# CVE-2021-37973: Google Chromium Portals Use-After-Free

> A remote attacker with compromised renderer access can escape the sandbox via a crafted HTML page due to a use-after-free in Portals.

- **Severity:** Critical 9.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Yes, since 3 Nov 2021 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 8 Oct 2021
- **Updated:** 21 Oct 2025
- **Also known as:** DEBIAN-CVE-2021-37973, GHSA-w2c8-qc3j-3xr5, UBUNTU-CVE-2021-37973

## What is CVE-2021-37973?

CVE-2021-37973 is a critical use after free vulnerability in Debian Debian Linux, published on 8 Oct 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-37973?

It affects 3 products.


Products: Debian Debian Linux, Fedoraproject Fedora, Google Chrome.

## How do I fix CVE-2021-37973?

Upgrade to a fixed version. US federal agencies must fix it by 17 Nov 2021.

## Is CVE-2021-37973 being exploited?

Yes. Attackers have exploited CVE-2021-37973 in the wild since at least 3 Nov 2021.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-37973 and fix it if it is affected.

What it is: CVE-2021-37973 is a critical use after free vulnerability in Debian Debian Linux, published on 8 Oct 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: Yes. Attackers have exploited CVE-2021-37973 in the wild since at least 3 Nov 2021.

Affected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-37973/ (Markdown: https://insights.sbomify.com/CVE-2021-37973/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-37973
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-37973
- OSV: https://osv.dev/vulnerability/CVE-2021-37973

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-37973/
Summaries are generated and may contain mistakes; the official description above is the record.