NibbleBlog 4.0.3 Shell Upload

`NibbleBlog 4.0.3: Code Execution  
Security Advisory – Curesec Research Team  
  
1. Introduction  
  
Affected Product: NibbleBlog 4.0.3   
Fixed in: not fixed  
Fixed Version Link: n/a   
Vendor Contact: Website: http://www.nibbleblog.com/   
Vulnerability Type: Code Execution   
Remote Exploitable: Yes   
Reported to vendor: 07/21/2015   
Disclosed to public: 09/01/2015   
Release mode: Full Disclosure   
CVE: n/a   
Credits Tim Coen of Curesec GmbH   
  
2. Vulnerability Description  
  
When uploading image files via the "My image" plugin - which is  
delivered with NibbleBlog by default - , NibbleBlog 4.0.3 keeps the  
original extension of uploaded files. This extension or the actual file  
type are not checked, thus it is possible to upload PHP files and gain  
code execution.  
  
Please note that admin credentials are required.  
  
3. Proof of Concept  
  
Obtain Admin credentials (for example via Phishing via XSS which can  
be gained via CSRF, see advisory about CSRF in NibbleBlog 4.0.3)  
Activate My image plugin by visiting  
http://localhost/nibbleblog/admin.php?controller=plugins&action=install&plugin=my_image  
Upload PHP shell, ignore warnings  
Visit  
http://localhost/nibbleblog/content/private/plugins/my_image/image.php.  
This is the default name of images uploaded via the plugin.  
  
4. Code  
  
  
if( $plugin->init_db() )  
{  
// upload files  
foreach($_FILES as $field_name=>$file)  
{  
$extension = strtolower(pathinfo($file['name'],  
PATHINFO_EXTENSION));  
$destination = PATH_PLUGINS_DB.$plugin->get_dir_name();  
$complete = $destination.'/'.$field_name.'.'.$extension;  
  
// Upload the new file and move  
if(move_uploaded_file($file["tmp_name"], $complete))  
{  
// Resize images if requested by the plugin  
if(isset($_POST[$field_name.'_resize']))  
{  
$width =  
isset($_POST[$field_name.'_width'])?$_POST[$field_name.'_width']:200;  
$height =  
isset($_POST[$field_name.'_height'])?$_POST[$field_name.'_height']:200;  
$option =  
isset($_POST[$field_name.'_option'])?$_POST[$field_name.'_option']:'auto';  
$quality =  
isset($_POST[$field_name.'_quality'])?$_POST[$field_name.'_quality']:100;  
  
$Resize->setImage($complete, $width, $height, $option);  
$Resize->saveImage($complete, $quality, true);  
}  
}  
}  
  
unset($_POST['plugin']);  
  
// update fields  
$plugin->set_fields_db($_POST);  
  
Session::set_alert($_LANG['CHANGES_HAS_BEEN_SAVED_SUCCESSFULLY']);  
}  
}  
  
5. Solution  
  
This issue was not fixed by the vendor.  
  
6. Report Timeline  
  
07/21/2015 Informed Vendor about Issue  
07/22/2015 Vendor Replied  
08/18/2015 Reminded Vendor of release date (no reply)  
09/01/2015 Disclosed to public  
  
7. Blog Reference  
http://blog.curesec.com/article/blog/NibbleBlog-403-Code-Execution-47.html  
  
  
`