# CVE-2021-20194: Memory corruption in kernel

> A local attacker can trigger a heap overflow in the Linux kernel BPF subsystem, potentially leading to privilege escalation or denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 23 Feb 2021
- **Updated:** 3 Aug 2024
- **Also known as:** AZL-34857, AZL-6529, DEBIAN-CVE-2021-20194, GHSA-vw35-vgjr-5jhv, UBUNTU-CVE-2021-20194

## What is CVE-2021-20194?

CVE-2021-20194 is a high-severity memory corruption vulnerability in Linux kernel, published on 23 Feb 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

There is a vulnerability in the linux kernel versions higher than 5.2 (if kernel compiled with config params CONFIG_BPF_SYSCALL=y , CONFIG_BPF=y , CONFIG_CGROUPS=y , CONFIG_CGROUP_BPF=y , CONFIG_HARDENED_USERCOPY not set, and BPF hook to getsockopt is registered). As result of BPF execution, the local user can trigger bug in __cgroup_bpf_run_filter_getsockopt() function that can lead to heap overflow (because of non-hardened usercopy). The impact of attack could be deny of service or possibly privileges escalation.

Weakness: CWE-787 (Out-of-bounds Write), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2021-20194?

It affects 3 products.


Products: Linux kernel, Redhat Enterprise Linux, Redhat Openshift Container Platform.

## How do I fix CVE-2021-20194?

Apply the vendor's patch.

## Is CVE-2021-20194 being exploited?

There is no known exploitation of CVE-2021-20194 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-2021-20194 and fix it if it is affected.

What it is: CVE-2021-20194 is a high-severity memory corruption vulnerability in Linux kernel, published on 23 Feb 2021. 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-2021-20194 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-2021-20194/ (Markdown: https://insights.sbomify.com/CVE-2021-20194/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-20194
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-20194
- OSV: https://osv.dev/vulnerability/CVE-2021-20194

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-20194/
Summaries are generated and may contain mistakes; the official description above is the record.