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e107 Arbitrary Variable Overwrite
Vendor: Steve Dunstan
Product: e107
Version: <= 0.7.11
BID: 30601
OSVDB: 47482
SECUNIA: 31394
e107 is a popular full featured content management system written in php. Unfortunately e107 suffers from an arbitrary variable overwriting issue within it's download.php file that allows a number of possible attacks to happen including, but possibly not limited to, arbitrary php code execution and SQL Injection. No authentication is required to exploit the issue and it can be exploited regardless of php magic quotes settings. All users are encouraged to upgrade their e107 installations as soon as possible.

Arbitrary Variable Overwriting
There is an arbitrary variable overwrite issue in download.php that is the result of unsafe usage of the php extract() function. Let's have a look at the code located in download.php @ lines 85-86

case 'list' :	// Category-based listing
if (isset($_POST['view'])) extract($_POST);

As we see from the above code it is very much possible to overwrite any variables declared up to this point, but what is the real risk here? What attacks are possible because of this issue?

view=1&id;=-99') UNION SELECT concat(user_name,char(58), user_password), 2,3,4 FROM e107_user WHERE user_id=1/*

One possible attack could involve an attacker sending a post request to the downloads category view page (download.php?list.1 for example) with the above data as the post contents, and as a result the username and pass hash will be displayed in the page title. This SQL Injection does require magic quotes to be set to it's default value of off.

view=1&action;=maincats&execute;=aWQ=&template;_load_core=echo%20exec (base64_decode($_POST[execute]));

In addition to the SQL Injection is an arbitrary php code execution vulnerability. I found that it is possible to execute arbitrary php code by sending a post request to the downloads category view page with the above data as the post contents. The above example will successfully execute the "id" shell command regardless if php magic quotes gpc settings. A valid download category must be available though, but this is trivial since an attacker can use the previously explained SQL Injection to gain admin credentials and add a download category. Other attacks may be possible though since a majority of the important variables within the script are at risk.

A fix for the issue mentioned in this advisory can be found in the public e107 CVS repository, or accessed directly at the link below.


James Bercegay of the GulfTech Security Research Team