# CVE-2021-28428: File upload in n/a

> Attacker can achieve remote code execution by uploading malicious .htaccess and .hello files to bypass PHP extension filters in HorizontCMS.

- **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:** No
- **Published:** 5 Apr 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-cm95-9q8x-72h6

## What is CVE-2021-28428?

CVE-2021-28428 is a critical vulnerability in n/a, published on 5 Apr 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

File upload vulnerability in HorizontCMS before 1.0.0-beta.3 via uploading a .htaccess and *.hello files using the Media Files upload functionality. The original file upload vulnerability (CVE-2020-27387) was remediated by restricting the PHP extensions; however, we confirmed that the filter was bypassed via uploading an arbitrary .htaccess and *.hello files in order to execute PHP code to gain RCE.

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

## Which versions are affected by CVE-2021-28428?

It affects 1 product.


Products: Horizontcms Project Horizontcms.

## How do I fix CVE-2021-28428?

No fix has been published for CVE-2021-28428 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-28428 being exploited?

There is no known exploitation of CVE-2021-28428 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2020-28693](https://insights.sbomify.com/CVE-2020-28693/): File upload in n/a (high 8.8)
- [CVE-2020-27387](https://insights.sbomify.com/CVE-2020-27387/): File upload in n/a (high 8.8)
- [CVE-2022-25104](https://insights.sbomify.com/CVE-2022-25104/): Path traversal in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-28428 and fix it if it is affected.

What it is: CVE-2021-28428 is a critical vulnerability in n/a, published on 5 Apr 2022. 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-2021-28428 in the wild and no public exploit code.

Affected product: n/a. 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-2021-28428/ (Markdown: https://insights.sbomify.com/CVE-2021-28428/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28428
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28428
- OSV: https://osv.dev/vulnerability/CVE-2021-28428

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28428/
Summaries are generated and may contain mistakes; the official description above is the record.