CVE-2018-20918 in cPanel
Summary
by MITRE
cPanel before 70.0.23 allows stored XSS in WHM DNS Cluster (SEC-372).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability CVE-2018-20918 represents a stored cross-site scripting flaw within cPanel's WHM DNS Cluster functionality, specifically affecting versions prior to 70.0.23. This security issue resides in the web-based management interface of cPanel, which is widely used by hosting providers and system administrators to manage their server environments. The vulnerability specifically targets the DNS cluster management component, which allows administrators to configure and manage distributed DNS services across multiple servers within a cluster environment. The flaw enables attackers to inject malicious scripts into the DNS cluster configuration data that will be executed whenever legitimate users access the affected interface. This represents a critical security risk as it can be exploited by attackers to gain unauthorized access to administrative functions or compromise the entire hosting infrastructure.
The technical implementation of this vulnerability stems from insufficient input validation and output sanitization within the DNS cluster management interface. When administrators configure DNS cluster settings, the system fails to properly sanitize user-supplied input before storing it in the database or rendering it in the web interface. This allows malicious actors to inject crafted JavaScript code through the DNS cluster configuration parameters, which are then stored persistently in the system. The vulnerability is classified as a stored XSS attack because the malicious payload is permanently stored within the application's data storage and executed whenever the affected page is loaded by legitimate users. The flaw demonstrates poor security practices in web application development and highlights the importance of implementing comprehensive input validation mechanisms. According to CWE classification, this vulnerability maps to CWE-79 which specifically addresses cross-site scripting flaws where untrusted data is improperly sanitized before being rendered in web pages. The vulnerability can be exploited through various attack vectors including direct manipulation of DNS cluster configuration data or through compromised administrative accounts.
The operational impact of CVE-2018-20918 extends beyond simple script execution, as it provides attackers with potential access to sensitive administrative functions within the cPanel environment. Successful exploitation could allow attackers to modify DNS records, create malicious domains, or even escalate privileges to gain full administrative control over the hosting infrastructure. The vulnerability affects hosting providers who rely on cPanel's DNS cluster functionality, potentially compromising thousands of domains managed through affected systems. Attackers could leverage this vulnerability to redirect traffic to malicious sites, steal sensitive data, or disrupt services for multiple customers simultaneously. The stored nature of the vulnerability means that the malicious scripts remain active even after the initial injection, creating a persistent threat that can affect any user who accesses the affected DNS cluster interface. This vulnerability also aligns with ATT&CK technique T1059.007 which covers command and script injection through web applications, demonstrating how attackers can use such flaws to maintain persistent access and execute malicious commands within the target environment.
Organizations should implement immediate mitigations to address this vulnerability by upgrading to cPanel version 70.0.23 or later, which contains the necessary patches to prevent the storage and execution of malicious scripts in the DNS cluster interface. System administrators should also conduct thorough security reviews of all DNS cluster configurations to identify any potential malicious entries that may have been previously injected. Network monitoring should be enhanced to detect unusual DNS query patterns that might indicate exploitation attempts. Additionally, implementing proper input validation controls and output encoding mechanisms in the web application framework can help prevent similar vulnerabilities from occurring in the future. The vulnerability serves as a reminder of the critical importance of regular security updates and proper security testing in web applications, particularly those handling sensitive administrative functions. Organizations should also consider implementing web application firewalls and security monitoring solutions that can detect and prevent XSS attacks targeting web-based management interfaces. The incident underscores the need for comprehensive security awareness training for system administrators who manage critical infrastructure components like cPanel and DNS services.