CVE-2018-20866 in cPanel
Summary
by MITRE
cPanel before 76.0.8 has Stored XSS in the WHM "Reset a DNS Zone" feature (SEC-461).
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Analysis
by VulDB Data Team • 07/15/2020
The vulnerability CVE-2018-20866 represents a stored cross-site scripting flaw within the cPanel web hosting control panel software, specifically affecting versions prior to 76.0.8. This security issue resides within the WHM (Web Host Manager) interface's "Reset a DNS Zone" functionality, making it accessible to authenticated users who possess appropriate privileges to execute DNS zone operations. The flaw allows an attacker with sufficient permissions to inject malicious JavaScript code into DNS zone data that persists in the system and executes when other users view the affected DNS zone information. This stored XSS vulnerability specifically targets the administrative interface of cPanel, which serves as a critical management component for web hosting providers and their clients. The vulnerability is classified under CWE-79 as a cross-site scripting flaw, where the malicious input is stored on the server and subsequently executed in the context of other users' browsers.
The technical exploitation of this vulnerability occurs when an attacker with access to the WHM interface can manipulate DNS zone data through the "Reset a DNS Zone" feature. When DNS zone information is reset or modified, the input validation fails to properly sanitize user-supplied data, allowing malicious script code to be stored within the DNS zone records. This stored malicious content becomes active when legitimate users access the DNS zone information through the WHM interface, causing the JavaScript code to execute in their browser context. The impact is particularly severe because WHM interfaces are typically accessed by system administrators and hosting providers who have elevated privileges, potentially enabling attackers to escalate their access and compromise entire hosting environments. This vulnerability directly maps to ATT&CK technique T1059.007 for Command and Scripting Interpreter, as it enables the execution of malicious scripts in user browsers, and T1548.002 for Abuse of Functionality, since it exploits legitimate administrative features for malicious purposes.
The operational impact of CVE-2018-20866 extends beyond simple script execution, as it can enable attackers to perform various malicious activities including credential theft, session hijacking, and data exfiltration from users accessing the affected WHM interface. Attackers could potentially steal administrator credentials, modify DNS records to redirect traffic to malicious sites, or execute additional attacks against the hosting infrastructure. The persistence of the stored payload makes this vulnerability particularly dangerous as it remains active until the affected DNS zones are manually cleaned or the cPanel software is updated. Organizations using cPanel versions prior to 76.0.8 face significant risk of unauthorized access and potential compromise of their hosting environments. The vulnerability demonstrates the critical importance of input validation and output encoding in administrative interfaces, as even legitimate features can become attack vectors when proper security controls are not implemented. This flaw underscores the necessity for regular security updates and the implementation of comprehensive security testing procedures for control panel software.
Organizations should immediately upgrade to cPanel version 76.0.8 or later to remediate this vulnerability, as the update includes proper input sanitization and output encoding mechanisms that prevent malicious script injection into DNS zone data. System administrators should also implement additional monitoring and logging of WHM interface activities, particularly around DNS zone modification operations, to detect potential exploitation attempts. The mitigation strategy should include regular security assessments of administrative interfaces, implementation of web application firewalls, and enforcement of strict input validation policies for all user-supplied data. Security teams should also consider implementing network segmentation and privilege separation to limit the potential impact of successful exploitation attempts. This vulnerability highlights the critical nature of maintaining up-to-date security patches for management interfaces and demonstrates how seemingly routine administrative features can become significant security risks when proper input validation is absent. The remediation process should also involve comprehensive testing of the updated software to ensure that the fix properly addresses the stored XSS vulnerability without introducing new issues.