Direct Static Code Injection

Description
Direct Static Code Injection attack consists on injecting code directly onto the resource used by application while processing a user request. This is normally performed by tampering libraries and template files which are created based on user input without proper data sanitization. Upon a user request to the modified resource, the actions defined on it will be executed at server side in the context of web server process.

Server Side Includes is considered a type of direct static code injection. It should not be confused with other types of code injection, like XSS (“Cross Site Scripting” or “HTML injection”) where the code is executed on client side.

Severity
High

Likelihood of exploitation
Medium to Low

Example 1
This is a simple example of exploitation of CGISCRIPT.NET csSearch 2.3 vulnerability, published on Bugtraq ID: 4368. By requesting the following URL to the server, it’s possible to execute commands defined on ‘’’’setup’’’ variable. csSearch.cgi?command=savesetup&setup=PERL_CODE_HERE For the classical example, it can be used the following command to remove all files from “/” folder: csSearch.cgi?command=savesetup&setup=`rm%20-rf%20/`

Note that the above command must be encoded in order to be accepted.

Example 2
This example exploits a vulnerability on Ultimate PHP Board (UPB) 1.9 (CVE-2003-0395), which allows an attacker to execute random php code. This happens because some user variables, like IP address and User-Agent, are stored in a file that is used by admin_iplog.php page to show user statistics. When an administrator browses this page, the previously injected code by a malicious request is executed. The following example stores a malicious PHP code that will deface index.html page when administrator browses admin_iplog.php. GET /board/index.php HTTP/1.0 User-Agent: <? system( "echo \'hacked\' > ../index.html" ); ?>

External references
http://www.seclab.tuwien.ac.at/advisories/TUVSA-0510-001.txt http://cve.mitre.org/docs/plover/SECTION.9.21.html#CODE.STAT http://marc.info/?l=bugtraq&m=105379741528925&w=2 http://archives.neohapsis.com/archives/bugtraq/2005-06/0002.html

Related Threats
Category:Command Execution

Related Attacks

 * Server Side Includes
 * Direct Dynamic Code Evaluation ('Eval Injection')

Related Vulnerabilities
Category:Input Validation Vulnerability

Related Countermeasures
Category:Input Validation