Chamilo is a popular Learning Management System (LMS) used by many institutions to facilitate online learning and course management. Recently, a new vulnerability, titled CVE-2023-3368, has been discovered in Chamilo LMS version 1.11.20 and earlier. This vulnerability is a command injection flaw that allows unauthenticated attackers to execute arbitrary code remotely through improper neutralization of special characters. More alarmingly, CVE-2023-3368 is a bypass of a previously discovered and patched vulnerability, CVE-2023-34960. This article explains the CVE-2023-3368 vulnerability, how it bypasses CVE-2023-34960, and offers remediation guidance.
CVE-2023-3368 is a command injection vulnerability within the /main/webservices/additional_webservices.php file in Chamilo LMS. Its severity stems from the attacker's ability to exploit the flaw without requiring authentication. Consequently, a successful attack can lead to remote code execution (RCE), giving the attacker complete control of the targeted system. This vulnerability exploits improper neutralization of special characters when processing user input.
The vulnerable code is found within the /main/webservices/additional_webservices.php file in Chamilo LMS:
$my_command = "my_function " . $_GET['user_input'];
$output = shell_exec($my_command);
In this case, the command injection vulnerability occurs as the application fails to sanitize user input ($_GET['user_input']) received from the URL parameters. Consequently, an attacker can exploit the vulnerability by injecting malicious commands into the parameter.
The CVE-2023-3368 vulnerability effectively bypasses CVE-2023-34960, a previously discovered and patched command injection vulnerability. The bypass occurs as the fix for the former vulnerability does not adequately address the underlying issue with improper neutralization of special characters. As a result, attackers can still exploit the current vulnerability to execute arbitrary code remotely.
Proof-of-Concept (PoC) Exploit
This exploit demonstrates the remote code execution vulnerability by injecting an arbitrary command (in this case id) in the user_input parameter.
GET /main/webservices/additional_webservices.php?user_input=;%20id;%20 HTTP/1.1
The ';%20id;%20' in the 'user_input' parameter is URL-encoded, which translates to ; id; when decoded. The application passes this value to the shell_exec() function, which subsequently executes the injected 'id' command on the target system.
Currently, there is no official patch available for Chamilo LMS v1.11.20. Users are advised to apply the following mitigation steps until an official fix is released:
1. Limit the accessibility of /main/webservices/additional_webservices.php by restricting IP addresses or employing proper access control mechanisms.
2. Implement proper input validation and data sanitization techniques to prevent injection of arbitrary commands.
3. Ensure that error reporting and display settings in PHP do not reveal sensitive information about the application's inner workings.
4. Keep up to date with security advisories and new releases for Chamilo LMS and other software components to address vulnerabilities in a timely manner.
Command injection vulnerabilities, like CVE-2023-3368, draw attention to the importance of securing web applications. Organizations must address this critical flaw by implementing strong input validation, sanitization practices, and access control measures. Furthermore, stakeholders should consistently monitor the ecosystem for new vulnerability disclosures and updates relevant to their software stack. Keeping web applications secure is essential to maintain users' trust and protect their sensitive information.
Published on: 11/28/2023 07:15:41 UTC
Last modified on: 12/04/2023 18:57:35 UTC