A critical security vulnerability has been discovered in ISPConfig version 3.2 build 12p1 that allows authenticated remote users to escalate their privileges to superadmin status and subsequently execute arbitrary PHP code on affected systems.
The vulnerability, identified by an independent security researcher working with SSD Secure Disclosure, exploits design flaws in the user creation and language modification functionalities of the popular web hosting control panel software.
ISPConfig Vulnerability Enables Privilege Escalation
The vulnerability stems from improper logic and validation of HTTP parameters in ISPConfig’s user edit functionality.
The system fails to adequately validate user roles when creating new accounts through the client_add method, allowing remote users with “Client Functions” enabled to create client accounts with admin module privileges.
The critical flaw occurs in the users_edit.php file, where a security check can be bypassed through parameter manipulation.
The system checks if typ == admin to prevent unauthorized admin user creation, but this validation only examines the first element of the typ[] array.
Attackers can circumvent this by sending a specially crafted request with parameters like typ=&typ[1]=admin, where the first parameter is empty and the second specifies the admin role.
The exploitation process involves three stages: first, creating a client user with an admin module enabled, then using that account to create an admin user by manipulating the typ[] parameter, and finally modifying the superadmin user (ID=1) to gain complete system control.
PHP Code Injection via Language Editor Vulnerability
Once superadmin privileges are obtained, attackers can exploit a second vulnerability in the language modification feature accessible through System > Language Editor > Languages.
This functionality allows arbitrary PHP code injection due to inadequate input validation that relies on a flawed regular expression pattern.
The vulnerable code uses the regex pattern /(^|[^\\\$$)((\\\\\\\$$*)”/” to escape double quotes in language file entries. However, this pattern fails to properly handle consecutive double quotes due to character consumption issues in the regex engine.
When processing strings containing consecutive quotes like Evil_Str””ing, only the first quote gets escaped while subsequent quotes remain unprocessed, enabling code injection.
The language files use .lng extensions and contain PHP code defining associative arrays with translations.
Since these files are directly included in the application code, successful injection allows arbitrary PHP execution with the privileges of the ISPConfig system user.
The vendor has disputed the severity of these vulnerabilities, claiming they require elevated privileges that pose no significant threat.
However, the research team argues that only admin privileges are needed rather than superadmin access, and admin privileges are commonly granted in corporate ISPConfig deployments.
The proof-of-concept demonstrates the complete attack chain, starting with a remote user account and ending with arbitrary code execution capabilities.
The vulnerabilities affect ISPConfig v3.2.12p1, with researchers indicating that previous versions likely contain the same flaws.
Organizations using ISPConfig should immediately review their user privilege assignments and consider implementing additional access controls until patches become available.
The combination of these vulnerabilities represents a significant security risk, particularly in multi-tenant hosting environments where client users are granted administrative access to manage their services.
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