# CVE-2021-4023: Denial of service in kernel

> A local user can crash the Linux kernel by triggering an improper cancellation in io-uring during free space shortages.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Mar 2022
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-4023, GHSA-rfvh-hg5j-x539, ROOT-OS-DEBIAN-11-CVE-2021-4023, UBUNTU-CVE-2021-4023

## What is CVE-2021-4023?

CVE-2021-4023 is a medium-severity denial of service vulnerability in Fedoraproject Fedora, published on 9 Mar 2022. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in the io-workqueue implementation in the Linux kernel versions prior to 5.15-rc1. The kernel can panic when an improper cancellation operation triggers the submission of new io-uring operations during a shortage of free space. This flaw allows a local user with permissions to execute io-uring requests to possibly crash the system.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2021-4023?

It affects 2 products.


Products: Fedoraproject Fedora, Linux kernel.

## How do I fix CVE-2021-4023?

Upgrade to a fixed version.

## Is CVE-2021-4023 being exploited?

There is no known exploitation of CVE-2021-4023 in the wild and no public exploit code.

## 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-2021-4023 and fix it if it is affected.

What it is: CVE-2021-4023 is a medium-severity denial of service vulnerability in Fedoraproject Fedora, published on 9 Mar 2022. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-4023 in the wild and no public exploit code.

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-2021-4023/ (Markdown: https://insights.sbomify.com/CVE-2021-4023/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4023
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4023
- OSV: https://osv.dev/vulnerability/CVE-2021-4023

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4023/
Summaries are generated and may contain mistakes; the official description above is the record.