# CVE-2021-36084: Use after free in n/a

> A use-after-free in the SELinux CIL compiler allows attackers to potentially execute arbitrary code or cause a denial of service.

- **Severity:** Low 3.3 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 1 Jul 2021
- **Updated:** 14 Oct 2026
- **Also known as:** DEBIAN-CVE-2021-36084, GHSA-8p9r-xrm6-68wq, UBUNTU-CVE-2021-36084

## What is CVE-2021-36084?

CVE-2021-36084 is a low-severity use after free vulnerability in Fedoraproject Fedora, published on 1 Jul 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

The CIL compiler in SELinux 3.2 has a use-after-free in __cil_verify_classperms (called from __cil_verify_classpermission and __cil_pre_verify_helper).

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-36084?

It affects 2 products.


Products: Fedoraproject Fedora, Selinux Project Selinux.

## How do I fix CVE-2021-36084?

Apply the vendor's patch.

## Is CVE-2021-36084 being exploited?

There is no known exploitation of CVE-2021-36084 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-2021-36084 and fix it if it is affected.

What it is: CVE-2021-36084 is a low-severity use after free vulnerability in Fedoraproject Fedora, published on 1 Jul 2021. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-36084 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-2021-36084/ (Markdown: https://insights.sbomify.com/CVE-2021-36084/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36084
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36084
- OSV: https://osv.dev/vulnerability/CVE-2021-36084

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-36084/
Summaries are generated and may contain mistakes; the official description above is the record.