PHPKit 1.6.6: Code Execution for Privileged Users8 Dec 2016 by Martin Bednorz
Today’s gift in our advent calendar contains PHPKit, a German web content management system in development since early 2002. With its ~42,000 lines of code it is a rather small application and the latest version is 1.6.6. This post describes two severe vulnerabilities in the administration section that require a minimal user permission for exploitation.
Within only 24 seconds, the analysis with RIPS completed and uncovered critical security vulnerabilities, mainly in the administration section of the application. As we demonstrated in multiple previous calendar posts, these vulnerabilities can be chained with other vulnerabilities that first escalate to administrative privileges and then allow to exploit these issues.
The truncated analysis results are available in our RIPS demo application. Please note that we limited the results to the issues described in this post since there are no fixes available.
Example 1: File Upload
The first vulnerability enables a malicious user to upload arbitrary files - including a PHP backdoor - that can be stored anywhere on the web server depending on its file permission configuration. The only requirement is that the attacker has access to a user account with the privilege to upload images which could be available, for example, for editorial staff. The following code lines are affected.
Here, the POST parameter
image_name is used completely unsanitized in the sensitive function
move_uploaded_file(). This allows an attacker to upload arbitrary files into the web root and thus, to execute custom PHP code on the targeted server. There is no file extension check as described and bypassed in our [previous calendar post](/2016/serendipity-from-file-upload-to-code-execution/. It is advised to not allow users to upload files into the web root and that the file name is not in full control of the uploading user.
Example 2: SQL Injection
The SQL injection in this example is rather simple and multiple similar issues exist across the application. The following lines of code are affected.
As shown in the code summaries above, the POST parameter
delete_links is not sanitized and used directly in the MySQL query in line 46. An attacker can easily break out of the quotes and alter the query by injecting SQL commands. This can be used to change arbitrary columns of the table or to extract user data. Since RIPS has to reconstruct the SQL query completely in order to evaluate the injection point, RIPS is also able to evaluate into which table’s columns an attacker is able to write a payload. This can then be used to detect second-order vulnerabilities, for example persistent XSS. The SQL injection vulnerability can be prevented by sanitizing the tainted variable
$_POST['delete_links'] using the function
mysql_real_escape_string() to hinder the attacker from breaking out of the quotes.
|2016/09/20||First contact with vendor|
|2016/09/20||Vendor discontinued development (no fixes are going to be published for the time being)|
RIPS was able to find many critical security vulnerabilities in a matter of seconds within the application. Even though the issues are located in the administration section of the application, the code execution could be exploited by editorial staff that should not have full access to the server or an attacker with escalated privileges. Unfortunately, the development is currently on hold so that no fixes are going to be made available. Hence, no security issues that help in escalating privileges are released. We advice all PHPKit administrators to remove unnecessary upload privileges and to harden the web server’s file permissions.
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Disclaimer: The information provided here is for educational purposes only. It is your responsibility to obey all applicable local, state and federal laws. RIPS Technologies GmbH assumes no liability and is not responsible for any misuse or damages caused by direct or indirect use of the information provided.