A newly identified vulnerability dubbed CVE-2023-41637 has been found in the "Carica immagine" function of GruppoSCAI RealGimm 1.1.37p38 web application, which poses a significant security risk. This arbitrary file upload vulnerability allows potential attackers to execute arbitrary code by simply uploading a carefully crafted HTML file. In this post, we will dissect the vulnerability, analyze the code responsible for the flaw, and discuss how to exploit and remediate the issue.

What is GruppoSCAI RealGimm?

GruppoSCAI RealGimm is a popular web application developed by GruppoSCAI. It's primarily used for managing images and various media files, making it a crucial component of many websites and content management systems.

Description of the Vulnerability

CVE-2023-41637 specifically impacts the Carica immagine function in the RealGimm 1.1.37p38 version. The vulnerability stems from a lack of proper file validation and sanitization, allowing attackers to upload arbitrary files, like malicious HTML files. Once uploaded, these files can be accessed and executed by the attacker, leading to potential unauthorized access, data compromise, and a wide range of malicious activities.

Reproducing the Exploit

To better understand the arbitrary file upload vulnerability and demonstrate how it can be exploited, let's walk through a sample code snippet showcasing the problematic code:

<?php
    // Carica immagine function
    function uploadImage($img) {
        // ...
        $file_extension = pathinfo($_FILES['image']['name'], PATHINFO_EXTENSION);
        // ...
        if (in_array($file_extension, $allowed_extensions)) { // Allowed file extensions: jpg, gif, png
            // ...
            move_uploaded_file($_FILES['image']['tmp_name'], $target_file);
        }
    }
?>

In this example, the application checks for allowed file extensions (jpg, gif, png) before moving the uploaded file ($target_file) to its final destination. However, an attacker can circumvent this validation by crafting an HTML file with an extension mentioned in the $allowed_extensions array, effectively bypassing the intended restriction.

Original References and Exploit Details

Link 1: CVE-2023-41637 - NVD
Link 2: Exploit Database - CVE-2023-41637

Mitigation and Remediation

The best approach to mitigate the risks associated with this vulnerability is to apply a security patch provided by the vendor, GruppoSCAI. Ensure that you are using the latest and most secure version of the RealGimm web application. Additionally, always follow secure coding practices and perform thorough security testing.

If a patch is not available, or you are unable to upgrade, consider implementing the following remediation steps:

1. Apply proper server-side validation and sanitization to uploaded files. Verify the file type and check file headers (not just the extension) to ensure it's the expected file format.

Limit the allowed file types to only the necessary formats for your application.

3. Implement a unique, unpredictable naming convention for uploaded files to prevent attackers from guessing the location of malicious files easily.
4. Restrict access to uploaded files and implement proper access controls to prevent unauthorized access.

Conclusion

Arbitrary file upload vulnerabilities like CVE-2023-41637 are critical security issues that can lead to devastating consequences if left unpatched or unaddressed. By understanding the exploit and remediation techniques outlined above, you can better protect your applications and systems from being compromised. Always strive to follow best practices, secure coding guidelines, and stay up-to-date with the latest security patches and updates from your software vendors.

Timeline

Published on: 08/31/2023 14:15:08 UTC
Last modified on: 09/06/2023 23:15:26 UTC