# CVE-2021-36440: Unrestricted File Upload in ShowDoc v2.9.5

> Remote attackers can execute arbitrary code by uploading malicious files via the file_url parameter in ShowDoc.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-c442-3278-rhrg

## What is CVE-2021-36440?

CVE-2021-36440 is a critical vulnerability in n/a, published on 8 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Unrestricted File Upload in ShowDoc v2.9.5 allows remote attackers to execute arbitrary code via the 'file_url' parameter in the component AdminUpdateController.class.php'.

Weakness: CWE-434 (Unrestricted Upload of File with Dangerous Type)

## Which versions are affected by CVE-2021-36440?

2 open source packages ship an affected version, including showdoc/showdoc. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `showdoc/showdoc` | Packagist | All versions | 2.9.6 |
| `showdoc/showdoc` | Packagist | All versions | 2.9.6 |

Products: Showdoc Showdoc.

## How do I fix CVE-2021-36440?

Upgrade showdoc/showdoc to 2.9.6 or later.

## Is CVE-2021-36440 being exploited?

There is no known exploitation of CVE-2021-36440 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-41745](https://insights.sbomify.com/CVE-2021-41745/): Showdoc File Upload Vulnerability (critical 9.8)
- [CVE-2022-0942](https://insights.sbomify.com/CVE-2022-0942/): Stored XSS due to Unrestricted File Upload in star7th/showdoc (critical 9.4)
- [CVE-2022-1034](https://insights.sbomify.com/CVE-2022-1034/): There is a Unrestricted Upload of File vulnerability in ShowDoc v2.10.3 in star7th/showdoc (critical 9.1)
- [CVE-2022-0945](https://insights.sbomify.com/CVE-2022-0945/): Stored XSS viva axd and cshtml file upload in star7th/showdoc in star7th/showdoc (critical 9.0)
- [CVE-2022-0965](https://insights.sbomify.com/CVE-2022-0965/): Stored XSS viva .ofd file upload in star7th/showdoc (critical 9.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-36440 and fix it if it is affected.

What it is: CVE-2021-36440 is a critical vulnerability in n/a, published on 8 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-36440 in the wild and no public exploit code.

Affected packages and fixed versions:
- showdoc/showdoc (Packagist): affected all versions; fixed in 2.9.6
- showdoc/showdoc (Packagist): affected all versions; fixed in 2.9.6

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-2021-36440/ (Markdown: https://insights.sbomify.com/CVE-2021-36440/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36440
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36440
- OSV: https://osv.dev/vulnerability/CVE-2021-36440

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-36440/
Summaries are generated and may contain mistakes; the official description above is the record.