CVE-2018-20902 in cPanel
Summary
by MITRE
cPanel before 71.9980.37 allows attackers to read root's crontab file by leveraging ClamAV installation (SEC-408).
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Analysis
by VulDB Data Team • 07/18/2020
This vulnerability exists within cPanel versions prior to 71.9980.37 and represents a critical privilege escalation flaw that allows unauthenticated attackers to access root's crontab file through the ClamAV installation component. The vulnerability stems from insufficient access controls and improper privilege management within the cPanel application's integration with ClamAV antivirus functionality. Attackers can exploit this weakness by leveraging the ClamAV installation process to gain unauthorized access to sensitive system configuration files that should only be accessible to root users.
The technical implementation of this vulnerability involves the improper handling of file permissions and access controls during the ClamAV installation process within cPanel environments. When ClamAV is installed or configured through cPanel, the system fails to properly enforce security boundaries between different user contexts, allowing attackers to manipulate file access patterns and retrieve the root crontab file. This represents a classic case of insufficient privilege separation and inadequate access control mechanisms. The flaw falls under CWE-276 which specifically addresses improper file permissions and inadequate access controls, while also demonstrating characteristics of CWE-732 which deals with inadequate protection of system resources.
The operational impact of this vulnerability is severe as the root crontab file contains critical system scheduling information including automated tasks, backup jobs, and potentially sensitive cron jobs that could provide attackers with insights into system administration practices and potentially reveal additional attack vectors. An attacker who successfully exploits this vulnerability gains access to system-level scheduling information that could be used for further exploitation, including identifying potential targets for privilege escalation or understanding system maintenance windows. The ability to read root crontab files can reveal administrative credentials, system monitoring configurations, and other sensitive operational details that would otherwise remain protected.
This vulnerability aligns with several tactics and techniques described in the MITRE ATT&CK framework, particularly in the privilege escalation and credential access domains. The attack pattern follows ATT&CK technique T1068 which involves local privilege escalation, and T1552 which covers credentials in files. The exploitation process typically involves leveraging the ClamAV installation interface to perform unauthorized file reads through the cPanel web interface, making it particularly dangerous as it requires no special authentication credentials. Organizations affected by this vulnerability should immediately implement patch management procedures to upgrade to cPanel version 71.9980.37 or later, which includes proper access control enforcement and privilege separation mechanisms. Additionally, system administrators should conduct thorough audits of cron job configurations and implement monitoring for unauthorized access attempts to critical system files.
The root cause of this vulnerability demonstrates the importance of proper privilege separation in web-based system management tools and highlights the risks associated with complex integration points between different system components. Security best practices recommend implementing least privilege principles and ensuring that all system interfaces properly validate access controls and enforce proper user permissions. This vulnerability serves as a reminder that even seemingly benign system components like antivirus installations can become attack vectors when proper security boundaries are not maintained. Organizations should also consider implementing additional monitoring and logging around file access patterns and system configuration changes to detect potential exploitation attempts. The fix implemented in cPanel 71.9980.37 addresses the core access control issue by enforcing proper privilege checks during ClamAV installation and file access operations, preventing unauthorized users from reading root-level system files through the web interface.