CVE-2021-21324

GLPI is an open-source asset and IT management software package that
provides ITIL Service Desk features, licenses tracking and software
auditing. In GLPI before version 9.5.4 there is an Insecure Direct Object
Reference (IDOR) on “Solutions”. This vulnerability gives an unauthorized
user the ability to enumerate GLPI items names (including users logins)
using the knowbase search form (requires authentication). To Reproduce:
Perform a valid authentication at your GLPI instance, Browse the ticket
list and select any open ticket, click on Solution form, then Search a
solution form that will redirect you to the endpoint
/“glpi/front/knowbaseitem.php?item_itemtype=Ticket&item_items_id=18&forcetab=Knowbase$1”,
and the item_itemtype=Ticket parameter present in the previous URL will
point to the PHP alias of glpi_tickets table, so just replace it with
“Users” to point to glpi_users table instead; in the same way,
item_items_id=18 will point to the related column id, so changing it too
you should be able to enumerate all the content which has an alias. Since
such id(s) are obviously incremental, a malicious party could exploit the
vulnerability simply by guessing-based attempts.