During the migration from Debian to Centos we figured out an issue that on CentOS the ldap search (same source, no changes there) returns also alias from subfolders within the search-dn.

We fixed this by changing zabbix/frontends/php/include/classes/ldap/CLdap.php in line 34 from:

'userfilter' => '(%{attr}=%{user})',

to

'userfilter' => '(&(ObjectClass=person)(%{attr}=%{user}))',

To avoid this changes everytime with an upgrade I would request adding the possibility to customizing the userfilter in Administration->Authentication.