Specially crafted string can cause a buffer overrun in the JSON parser library leading to a crash of the Zabbix Server or a Zabbix Proxy.

After the initial setup process, some steps of setup.php file are reachable not only by super-administrators, but by unauthenticated users as well. Malicious actor can pass step checks and potentially change the configuration of Zabbix Frontend.

An authenticated user can create a hosts group from the configuration with XSS payload, which will be available for other users. When XSS is stored by an authenticated malicious actor and other users try to search for groups during new host creation, the XSS payload will fire and the actor can steal session cookies and perform session hijacking to impersonate users or take over their accounts.

During Zabbix installation from RPM, DAC_OVERRIDE SELinux capability is in use to access PID files in [/var/run/zabbix] folder. In this case, Zabbix Proxy or Server processes can bypass file read, write and execute permissions check on the file system level

In the case of instances where the SAML SSO authentication is enabled (non-default), session data can be modified by a malicious actor, because a user login stored in the session was not verified. Malicious unauthenticated actor may exploit this issue to escalate privileges and gain admin access to Zabbix Frontend. To perform the attack, SAML authentication is required to be enabled and the actor has to know the username of Zabbix user (or use the guest account, which is disabled by default).