# CVE-2021-4021: Denial of service in radare2

> Attackers can cause denial of service in Radare2 by mapping huge zero-filled sections in MIPS ELF64 binaries, leading to uncontrolled resource consumption.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Feb 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-4g55-4fxv-2g82, UBUNTU-CVE-2021-4021

## What is CVE-2021-4021?

CVE-2021-4021 is a high-severity denial of service vulnerability in Radare Radare2, published on 24 Feb 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was found in Radare2 in versions prior to 5.6.2, 5.6.0, 5.5.4 and 5.5.2. Mapping a huge section filled with zeros of an ELF64 binary for MIPS architecture can lead to uncontrolled resource consumption and DoS.

Weakness: CWE-834 (Excessive Iteration), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2021-4021?

It affects 1 product.


Products: Radare Radare2.

## How do I fix CVE-2021-4021?

Upgrade to a fixed version.

## Is CVE-2021-4021 being exploited?

There is no known exploitation of CVE-2021-4021 in the wild and no public exploit code.

## Other vulnerabilities in Radare Radare2

- [CVE-2025-1864](https://insights.sbomify.com/CVE-2025-1864/): Buffer Overflow and Potential Code Execution in Radare2 (critical 10.0)
- [CVE-2025-1744](https://insights.sbomify.com/CVE-2025-1744/): Out-of-bounds Write in radare2 (critical 10.0)
- [CVE-2021-32494](https://insights.sbomify.com/CVE-2021-32494/): Denial of service in radare2 (critical 10.0)
- [CVE-2021-32495](https://insights.sbomify.com/CVE-2021-32495/): Use after free in radare2 (critical 10.0)
- [CVE-2024-29646](https://insights.sbomify.com/CVE-2024-29646/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4021 and fix it if it is affected.

What it is: CVE-2021-4021 is a high-severity denial of service vulnerability in Radare Radare2, published on 24 Feb 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-4021 in the wild and no public exploit code.

Affected product: Radare Radare2. 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-2021-4021/ (Markdown: https://insights.sbomify.com/CVE-2021-4021/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4021
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4021
- OSV: https://osv.dev/vulnerability/CVE-2021-4021

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4021/
Summaries are generated and may contain mistakes; the official description above is the record.