Problem CKFinder with multilingual site
set the $cookie_domain variable in sites/default/settings.php 

&lt;?php
$cookie_domain = $_SERVER['SERVER_NAME'];
?&gt;


Uncomment the $base_url variable and set the base URL of your website (without the trailing slash).

Another option if you have the Drupal Domain access module installed use

&lt;?php
$base_domain = explode('.', $_SERVER['SERVER_NAME']);
unset($base_domain[0]);
$base_domain = '.' . implode($base_domain, '.');

$cookie_domain = $base_domain;
?&gt;


Here is the reference to the answer