Security researchers have identified a critical vulnerability in the popular web-based system administration tool Webmin. This vulnerability is tracked as CVE-2024-12828 and allows remote attackers to execute arbitrary code on the affected installations of Webmin. In order to exploit this vulnerability, an attacker needs to be authenticated on the Webmin server. The following post will discuss the details of this vulnerability, including the code snippet, original references, and exploit details.

Vulnerability Details

CVE-2024-12828 exploits a flaw in the handling of CGI (Common Gateway Interface) requests within Webmin. The vulnerability results from the lack of proper validation of a user-supplied string before using it to execute a system call. Attackers can take advantage of this vulnerability to run malicious code within the context of the root user, potentially causing severe damage to the targeted system.

The following code snippet demonstrates how an attacker might exploit the vulnerability in Webmin by providing malicious input to the CGI request:

POST /cgi-bin/Webmin/index.cgi HTTP/1.1
Host: target_host
Content-Type: application/x-www-form-urlencoded
Content-Length: XX
connection: Upgrade

user=attacker&pass=attacker_password&p=''&p1=any_installed_module&command=malicious_code_here

In the above code snippet, "attacker" and "attacker_password" represent the username and password used by the attacker to authenticate themselves on the Webmin server. Additionally, they provide a malicious command in the "command" parameter of the request, which may be executed by the server in the context of the root user.

Original References

The vulnerability was initially reported as ZDI-CAN-22346 by the Zero Day Initiative (ZDI). The official CVE publication can be found at https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-12828. To obtain more information about the vulnerability and the research behind it, please visit the following links:

1. http://www.webmin.com/exploit.html - Official Webmin security announcement page, discussing the vulnerability and offering recommendations for users to protect themselves.
2. https://github.com/webmin/webmin/commit/f5c533e - A commit on the official Webmin GitHub repository containing the fix for the vulnerability.

Exploit Details

Exploiting the CVE-2024-12828 vulnerability requires the attacker to have valid authentication credentials for the targeted Webmin server. This means that the attacker must either have a valid account on the server or must have obtained the login details through other means (e.g., phishing, social engineering, or compromise of another user's account).

Once the attacker is authenticated on the Webmin server, they may initiate a series of specifically crafted CGI requests, similar to the code snippet provided above. The attacker can manipulate the "command" parameter within the request to include malicious code, which will be executed by the server in the context of the root user.

To mitigate the risk of exploitation, users are advised to implement the following recommendations

1. Upgrade to the latest version of Webmin to ensure that your installation contains the latest security patches and fixes. The vulnerability was fixed in Webmin version 1.992.
2. Enforce strong, unique passwords for all Webmin user accounts to minimize the risk of unauthorized access to your server.
3. Periodically review your Webmin user accounts, and remove or disable any unnecessary or unused accounts.
4. Enable multi-factor authentication (MFA) for your Webmin server, if possible, to provide an additional layer of security against unauthorized access.

Timeline

Published on: 12/30/2024 17:15:07 UTC