# CVE-2021-4203: Use after free in kernel

> A local attacker can trigger a race condition to crash the system or leak kernel information via a use-after-free flaw in socket options.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Mar 2022
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-4203, GHSA-rh28-76xv-jcqc, UBUNTU-CVE-2021-4203

## What is CVE-2021-4203?

CVE-2021-4203 is a medium-severity use after free vulnerability in Linux kernel, published on 25 Mar 2022. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A use-after-free read flaw was found in sock_getsockopt() in net/core/sock.c due to SO_PEERCRED and SO_PEERGROUPS race with listen() (and connect()) in the Linux kernel. In this flaw, an attacker with a user privileges may crash the system or leak internal kernel information.

Weakness: CWE-416 (Use After Free), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2021-4203?

It affects 16 products.


Products: Linux kernel, Netapp A700s Firmware, Netapp Active Iq Unified Manager, Netapp Bootstrap Os, Netapp E-Series Santricity Os Controller, Netapp Element Software, Netapp H300s Firmware, Netapp H410c Firmware, Netapp H410s Firmware, Netapp H500s Firmware, Netapp H700s Firmware, Netapp Hci Management Node, Netapp Solidfire, Oracle Communications Cloud Native Core Binding Support Function, Oracle Communications Cloud Native Core Network Exposure Function, Oracle Communications Cloud Native Core Policy.

## How do I fix CVE-2021-4203?

Apply the vendor's patch.

## Is CVE-2021-4203 being exploited?

There is no known exploitation of CVE-2021-4203 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4203 and fix it if it is affected.

What it is: CVE-2021-4203 is a medium-severity use after free vulnerability in Linux kernel, published on 25 Mar 2022. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-4203 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2021-4203/ (Markdown: https://insights.sbomify.com/CVE-2021-4203/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4203
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4203
- OSV: https://osv.dev/vulnerability/CVE-2021-4203

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4203/
Summaries are generated and may contain mistakes; the official description above is the record.