# CVE-2021-21220: Google Chromium V8 Improper Input Validation

> A remote attacker can exploit heap corruption in the V8 engine via a crafted HTML page, potentially executing arbitrary code.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/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:** 26 Apr 2021
- **Updated:** 21 Oct 2025
- **Also known as:** CLEANSTART-2024-WN69569, DEBIAN-CVE-2021-21220, GHSA-5cw9-vvr5-jcwf, UBUNTU-CVE-2021-21220

## What is CVE-2021-21220?

CVE-2021-21220 is a high-severity memory corruption vulnerability in Fedoraproject Fedora, published on 26 Apr 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

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.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-21220?

It affects 2 products.


Products: Fedoraproject Fedora, Google Chrome.

## How do I fix CVE-2021-21220?

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

## Is CVE-2021-21220 being exploited?

Yes. Attackers have exploited CVE-2021-21220 in the wild since at least 3 Nov 2021.

Public exploit code:

- https://github.com/AmesianX/CVE-2021-21220 (github_poc): https://github.com/AmesianX/CVE-2021-21220
- Google Chrome versions before 89.0.4389.128 V8 XOR Typer Out-Of-Bounds Access RCE (metasploit)
- https://github.com/JacobTaylor3/CVE-2021-21220 (github_poc): https://github.com/JacobTaylor3/CVE-2021-21220
- CVE-2021-21220 Exploitation infrastructure  (github_poc): https://github.com/JacobTaylor3/C2-and-Post-Exploitation-Framework
- https://github.com/borahll/CVE-2021-21220 (github_poc): https://github.com/borahll/CVE-2021-21220

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-21220 and fix it if it is affected.

What it is: CVE-2021-21220 is a high-severity memory corruption vulnerability in Fedoraproject Fedora, published on 26 Apr 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-2021-21220 in the wild since at least 3 Nov 2021.

Affected product: Fedoraproject Fedora. 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-2021-21220/ (Markdown: https://insights.sbomify.com/CVE-2021-21220/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-21220
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-21220
- OSV: https://osv.dev/vulnerability/CVE-2021-21220

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-21220/
Summaries are generated and may contain mistakes; the official description above is the record.