ISPConfig Vulnerability Allows Privilege Escalation to Superadmin and PHP Code Injection Exploit

A critical security vulnerability has been identified in ISPConfig version 3.2.12p1, a widely used open-source web hosting control panel.

The vulnerability allows authenticated attackers to escalate their privileges to that of a superadmin and execute arbitrary PHP code remotely, posing a serious risk to affected systems.

The vulnerability primarily originates from design Vulnerability in ISPConfig’s user creation and editing functionality.

Under normal circumstances, ISPConfig segregates users into several roles: clients, resellers, admins, and a unique superadmin.

Attackers with access as “Remote Users” and client functionalities enabled, can manipulate HTTP parameters when using the client_add and users_edit features.

By exploiting inadequate validation logic, a remote user can create a client account with admin privileges—something that should not be allowed.

The core of the flaw is the improper checking of the typ[] parameter array, which, if crafted maliciously, enables the bypass of the intended security restriction.

Specifically, the code only inspects the first element of the typ[] array for admin status, enabling attackers to pass typ=&typ1=admin and thereby slip past validation.

This escalation process allows an adversary to first create an admin user from a client session.

A proof-of-concept attack involves sending a POST request to the /admin/language_edit.php endpoint containing a malicious payload, such as an entry ending with ";phpinfo();//, which the faulty regex fails to fully neutralize.

Then, using the same loophole with the newly created admin credentials, the attacker is able to modify or assume the identity of the superadmin user (ID 1), effectively granting themselves unrestricted access to the ISPConfig instance.

ISPConfig Vulnerability

Once superadmin privileges are obtained, a second critical Vulnerability becomes exploitable. The “language modification” feature within the control panel allows administrators to edit system language files, which are implemented as PHP arrays.

However, an oversight in the PHP code responsible for escaping user inputs in these files allows for insufficient sanitization of double quotes using a flawed regex.

This improper escaping permits a sophisticated attacker to inject arbitrary PHP code into the language file.

Since ISPConfig includes these files across its interface, the injected PHP gets executed in the context of the web application—directly leading to remote code execution on the server.

Then, using the same loophole with the newly created admin credentials, the attacker is able to modify or assume the identity of the superadmin user (ID 1), effectively granting themselves unrestricted access to the ISPConfig instance.

This results in the execution of arbitrary commands whenever the tainted language string is loaded.

Vendor Response and Security Implications

According to Report, the vulnerability was discovered by an independent security researcher collaborating with SSD Secure Disclosure.

While the vendor acknowledges the presence of these vulnerability, ISPConfig maintains that their impact is limited since exploitation requires admin-level access, which organizations are expected to tightly control.

However, the researchers argue that admin rights are commonly granted and that the privilege escalation chain lowers the bar for exploitation significantly.

This vulnerability affects ISPConfig version 3.2.12p1 on all supported platforms, with very high likelihood that earlier versions are similarly vulnerable.

System administrators are strongly urged to review privilege allocation, monitor user activity, and apply patches or mitigations as soon as they become available.

Until a fix is issued, the chain of privilege escalation and code execution poses a substantial risk for compromise and server takeover.

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