CVE-2018-20948 in cPanel
Summary
by MITRE
cPanel before 68.0.27 allows self XSS in cPanel Backup Restoration (SEC-383).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2018-20948 represents a critical self-cross-site scripting flaw within cPanel software versions prior to 68.0.27. This security weakness specifically affects the cPanel Backup Restoration functionality, creating a dangerous condition where authenticated users can execute malicious scripts against themselves. The issue stems from insufficient input validation and output sanitization mechanisms within the backup restoration interface, allowing attackers who have gained access to a user account to inject malicious JavaScript code that executes in the context of the victim's session. This type of vulnerability falls under the CWE-79 category of Cross-Site Scripting, specifically classified as self-XSS where the attack vector targets the user's own browser session rather than external parties.
The technical exploitation of this vulnerability occurs when a malicious actor with access to a cPanel account crafts specially formatted backup restoration parameters that contain embedded JavaScript payloads. When the victim navigates to the backup restoration interface and processes these malicious inputs, the injected scripts execute in the victim's browser context with the privileges of their authenticated session. This creates a dangerous scenario where the attacker can potentially steal session cookies, modify account settings, access sensitive data, or perform unauthorized actions that the victim is authorized to perform. The vulnerability's impact is particularly severe because it leverages the victim's own authenticated session, making it difficult to detect and trace back to the original attacker. The attack follows the typical pattern described in the ATT&CK framework under T1059.007 for Scripting and T1531 for Account Access and Use, where the adversary exploits legitimate access to execute malicious code.
The operational consequences of CVE-2018-20948 extend beyond simple data theft or session hijacking. Attackers can use this vulnerability to establish persistent access to compromised accounts by creating backdoors through the backup restoration functionality, which is often used regularly by system administrators. The vulnerability affects the integrity of the cPanel environment by allowing unauthorized modification of backup restoration processes, potentially leading to data corruption or the installation of malicious software through compromised backup files. Organizations using older cPanel versions face significant risk as attackers can leverage this vulnerability to escalate privileges within their hosting environments, potentially compromising multiple accounts on shared hosting platforms. The self-XSS nature of the vulnerability also makes it particularly challenging to detect through traditional network monitoring tools since the malicious activity occurs within the user's browser rather than through network traffic. Security teams must implement comprehensive monitoring of backup restoration activities and user account behaviors to identify potential exploitation attempts.
Mitigation strategies for CVE-2018-20948 require immediate patching of cPanel installations to version 68.0.27 or later, which includes proper input validation and output encoding mechanisms that prevent the execution of malicious scripts. Organizations should implement additional security controls such as regular security audits of backup restoration processes, enhanced user session management, and monitoring of unusual backup restoration activities. The implementation of Content Security Policy headers can provide an additional layer of protection against script execution, while regular security training for administrators can help prevent social engineering attacks that might lead to account compromise. System administrators should also consider implementing multi-factor authentication and privileged access management controls to limit the impact of potential account takeovers. The vulnerability highlights the importance of maintaining up-to-date software versions and implementing defense-in-depth strategies that protect against various attack vectors within complex hosting environments. Organizations should conduct regular vulnerability assessments targeting their cPanel installations and ensure that all backup restoration functionalities are properly secured against both external and internal threats.