# CVE-2021-36087: Memory corruption in n/a

> A heap-based buffer over-read in the SELinux CIL compiler allows attackers to cause denial of service or disclose sensitive memory contents via invalid optional block statements.

- **Severity:** Low 3.3 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **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:** 1 Jul 2021
- **Updated:** 14 Oct 2026
- **Also known as:** DEBIAN-CVE-2021-36087, GHSA-xjc2-37xp-26m5, UBUNTU-CVE-2021-36087

## What is CVE-2021-36087?

CVE-2021-36087 is a low-severity memory corruption vulnerability in Fedoraproject Fedora, published on 1 Jul 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The CIL compiler in SELinux 3.2 has a heap-based buffer over-read in ebitmap_match_any (called indirectly from cil_check_neverallow). This occurs because there is sometimes a lack of checks for invalid statements in an optional block.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2021-36087?

It affects 2 products.


Products: Fedoraproject Fedora, Selinux Project Selinux.

## How do I fix CVE-2021-36087?

Apply the vendor's patch.

## Is CVE-2021-36087 being exploited?

There is no known exploitation of CVE-2021-36087 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-2021-36087 and fix it if it is affected.

What it is: CVE-2021-36087 is a low-severity memory corruption vulnerability in Fedoraproject Fedora, published on 1 Jul 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-2021-36087 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-2021-36087/ (Markdown: https://insights.sbomify.com/CVE-2021-36087/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36087
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36087
- OSV: https://osv.dev/vulnerability/CVE-2021-36087

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-36087/
Summaries are generated and may contain mistakes; the official description above is the record.