CVE-2018-20950 in cPanel
Summary
by MITRE
cPanel before 68.0.27 allows self stored XSS in WHM Account Transfer (SEC-386).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability CVE-2018-20950 represents a stored cross-site scripting flaw in cPanel software versions prior to 68.0.27, specifically affecting the WHM Account Transfer functionality. This security weakness enables authenticated attackers with access to WHM (Web Host Manager) to inject malicious scripts into the system that persist and execute when other users view affected pages. The vulnerability falls under the category of stored XSS attacks as described by CWE-079, where malicious input is stored on the server and subsequently served to other users without proper sanitization or encoding. The affected WHM Account Transfer feature processes user-provided data that is not adequately validated or escaped, creating an environment where attacker-controlled content can be embedded within the application's response.
The technical exploitation of this vulnerability occurs within the WHM interface where administrators manage account transfers between hosting environments. When transferring accounts, the system accepts input parameters that are stored in the database or configuration files without proper sanitization. An attacker with WHM access can craft malicious payloads that include script tags or other XSS vectors, which are then stored in the system. These payloads execute in the context of other users' browsers who view the affected pages, potentially allowing for session hijacking, credential theft, or redirection to malicious sites. The vulnerability is particularly concerning in shared hosting environments where multiple administrators may have WHM access, as it could enable lateral movement within the hosting infrastructure.
The operational impact of CVE-2018-20950 extends beyond simple script execution, as it can compromise the integrity of the entire hosting environment. Attackers can leverage this vulnerability to establish persistent access to compromised accounts, potentially escalating privileges or accessing sensitive customer data. The stored nature of the vulnerability means that the malicious code remains active even after the initial attack, creating a long-term threat vector that can be exploited repeatedly. This weakness aligns with ATT&CK technique T1566.002 for credential access through phishing and can be combined with other attack vectors to create more sophisticated compromise scenarios. The vulnerability affects the confidentiality, integrity, and availability of hosting services, particularly impacting the trust relationship between hosting providers and their customers.
Mitigation strategies for CVE-2018-20950 require immediate patching of affected cPanel installations to version 68.0.27 or later, which includes proper input validation and output encoding for the WHM Account Transfer functionality. Organizations should implement comprehensive access controls and privilege management to limit WHM access to only essential personnel, following the principle of least privilege as recommended by security frameworks. Input sanitization measures should be strengthened throughout the application, particularly for user-provided data that is stored in the system, with proper HTML escaping and content security policies implemented. Network monitoring should be enhanced to detect suspicious activities related to account transfers, and regular security assessments should be conducted to identify similar vulnerabilities in other components of the hosting infrastructure. Additionally, implementing multi-factor authentication for administrative access and regular security training for system administrators can help reduce the risk of exploitation and improve overall security posture.