CVE-2005-2021 in cPanel
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in cPanel 9.1 and earlier allows remote attackers to inject arbitrary web script or HTML via the user parameter in the login page.
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Analysis
by VulDB Data Team • 06/03/2025
The vulnerability described in CVE-2005-2021 represents a critical cross-site scripting flaw within cPanel version 9.1 and earlier installations. This security weakness resides in the authentication mechanism of the web-based control panel, specifically targeting the login page's handling of user input parameters. The vulnerability manifests when the application fails to properly sanitize or validate the user parameter, creating an opening for malicious actors to execute arbitrary web scripts or HTML code within the context of other users' browsers.
This particular XSS vulnerability operates through a classic reflected attack vector where an attacker crafts a malicious URL containing script code within the user parameter. When an unsuspecting user clicks such a link and is directed to the vulnerable cPanel login page, the malicious payload executes in their browser session. The flaw stems from inadequate input validation and output encoding practices within the web application's user interface components, allowing attacker-controlled data to be interpreted as executable code rather than benign text input.
The operational impact of this vulnerability extends beyond simple script injection, potentially enabling attackers to hijack user sessions, steal authentication credentials, or perform unauthorized actions within the compromised cPanel environment. Given that cPanel serves as a critical administrative interface for web hosting environments, successful exploitation could lead to complete compromise of hosting accounts, unauthorized access to website files, database manipulation, and potential lateral movement within network infrastructure. The vulnerability affects not just individual user sessions but could also enable attackers to establish persistent access points within hosting environments where multiple customers share the same infrastructure.
Security practitioners should note this vulnerability aligns with CWE-79 which defines cross-site scripting as a weakness where untrusted data is sent to a web browser without proper validation or encoding. The attack pattern follows established techniques documented in MITRE ATT&CK framework under TA0001 Initial Access and TA0002 Execution domains, where attackers leverage web application vulnerabilities to establish footholds and execute malicious code. Organizations should implement immediate mitigations including input sanitization of all user parameters, output encoding for dynamic content, and deployment of web application firewalls to detect and block malicious payloads. The most effective remediation involves upgrading to cPanel versions that have addressed this vulnerability through proper input validation and output encoding mechanisms, along with implementing comprehensive security monitoring to detect potential exploitation attempts.