CVE-2018-20899 in cPanel
Summary
by MITRE
cPanel before 71.9980.37 allows stored XSS in the WHM cPAddons installation interface (SEC-398).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2018-20899 represents a stored cross-site scripting flaw within the cPanel software ecosystem, specifically affecting versions prior to 71.9980.37. This security weakness resides within the WHM cPAddons installation interface, which serves as a critical component for managing third-party software installations on cPanel hosting environments. The vulnerability stems from insufficient input validation and output sanitization mechanisms that fail to properly handle malicious user-supplied data within the addon installation process. Attackers can exploit this flaw by injecting malicious JavaScript code through the addon installation interface, which then gets stored on the server and executed whenever authorized users access the affected interface.
The technical implementation of this stored XSS vulnerability occurs when the WHM cPAddons interface fails to properly escape or filter user-controllable parameters during the addon installation process. When administrators or users interact with the installation interface, the system processes and displays user inputs without adequate sanitization measures, creating an environment where malicious scripts can be persisted and executed in the context of authenticated user sessions. This flaw operates under CWE-79 which categorizes cross-site scripting vulnerabilities as weaknesses in input validation and output encoding, specifically targeting the failure to properly escape output data. The vulnerability allows attackers to execute arbitrary JavaScript code within the browser of authenticated users who access the compromised interface, potentially leading to session hijacking, privilege escalation, or data exfiltration.
The operational impact of CVE-2018-20899 extends beyond simple script execution, as it provides attackers with a persistent foothold within hosting environments managed through cPanel. When exploited successfully, this vulnerability enables attackers to manipulate the cPAddons interface to install malicious software packages, modify existing installations, or redirect users to phishing sites. The stored nature of the vulnerability means that the malicious payloads remain active even after the initial injection, continuously affecting any user who accesses the compromised interface. This characteristic aligns with ATT&CK technique T1059.007 which describes the use of scripting languages for execution, and T1566 which covers social engineering through malicious content. The vulnerability particularly impacts hosting providers and their customers who rely on cPanel for web hosting management, as successful exploitation can compromise multiple accounts and potentially lead to broader system compromise.
Organizations affected by this vulnerability should implement immediate mitigations including updating to cPanel version 71.9980.37 or later, which contains the necessary patches to address the XSS flaw. Security administrators should also consider implementing additional protective measures such as web application firewalls that can detect and block malicious payloads targeting the cPAddons interface. The remediation process should include thorough auditing of existing installations to identify any compromised interfaces or malicious installations that may have been introduced through exploitation of this vulnerability. Regular security monitoring and input validation testing should be implemented to prevent similar vulnerabilities from emerging in other components of the cPanel ecosystem. Additionally, organizations should consider implementing principle of least privilege controls and regular security assessments to reduce the attack surface and improve overall security posture against similar stored XSS threats.