CVE-2018-20868 in cPanel
Summary
by MITRE
cPanel before 76.0.8 has Stored XSS in the WHM MultiPHP Manager interface (SEC-464).
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 07/15/2020
The vulnerability identified as CVE-2018-20868 represents a critical stored cross-site scripting flaw within the cPanel WHM MultiPHP Manager interface, affecting versions prior to 76.0.8. This security weakness resides in the web hosting control panel's administrative interface, specifically within the MultiPHP Manager module that allows administrators to configure php.ini settings for multiple PHP versions simultaneously. The flaw enables attackers to inject malicious scripts that persist in the application's database and execute whenever the affected interface is accessed by legitimate users. The vulnerability is particularly concerning as it operates within the WHM (Web Host Manager) context, which provides administrative privileges to system administrators, making the potential impact significantly more severe than typical user-facing XSS vulnerabilities.
The technical implementation of this stored XSS vulnerability stems from insufficient input validation and output sanitization within the MultiPHP Manager's parameter handling mechanisms. When administrators or users interact with the interface to manage PHP configurations, the application fails to properly sanitize user-supplied data before storing it in the database. This allows malicious actors to submit crafted payloads through various input fields within the MultiPHP Manager, which are then stored and subsequently executed in the context of other users' browsers who access the compromised interface. The vulnerability operates under CWE-79 which specifically addresses cross-site scripting flaws, and it aligns with ATT&CK technique T1190 which covers exploitation of vulnerabilities in web applications. The persistence of the malicious script in the database means that the payload executes automatically whenever the affected interface is loaded, making it particularly dangerous for administrative interfaces where privileged users regularly access the system.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the capability to escalate privileges and potentially compromise entire hosting environments. An attacker who successfully exploits this vulnerability can execute arbitrary JavaScript code in the context of the victim's browser, enabling them to steal session cookies, perform actions on behalf of the authenticated user, or redirect victims to malicious sites. In the context of WHM administration, this could allow an attacker to gain access to sensitive hosting configurations, modify user accounts, or even compromise the underlying server infrastructure. The vulnerability's presence in a system administration interface means that successful exploitation could lead to complete system compromise, particularly when combined with other attack vectors or when the compromised administrator has elevated privileges. The stored nature of the vulnerability means that the malicious code remains active even after the initial injection, creating a persistent threat that can affect multiple users over time.
Mitigation strategies for CVE-2018-20868 focus primarily on immediate patching and implementation of additional security controls. Organizations must upgrade to cPanel version 76.0.8 or later, which contains the necessary fixes to address the stored XSS vulnerability in the MultiPHP Manager interface. Beyond patching, administrators should implement additional security measures including input validation controls, output encoding, and regular security audits of web application interfaces. The implementation of Content Security Policy headers can provide additional protection against XSS attacks by restricting the sources from which scripts can be loaded. Network segmentation and privilege separation should be maintained to limit the potential impact of successful exploitation attempts. Regular security monitoring and log analysis can help detect potential exploitation attempts, while comprehensive backup strategies ensure that systems can be restored quickly in case of successful compromise. Organizations should also consider implementing web application firewalls to provide additional layers of protection against similar vulnerabilities. The vulnerability serves as a reminder of the critical importance of keeping web hosting control panels updated and maintaining robust security practices in administrative interfaces where privileged access is granted.