CVE-2018-20943 in cPanel
Summary
by MITRE
cPanel before 68.0.27 allows attackers to read root's crontab file during a short time interval upon a post-update task (SEC-352).
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Analysis
by VulDB Data Team • 07/18/2020
This vulnerability exists within cPanel software versions prior to 68.0.27, representing a critical privilege escalation and information disclosure flaw that directly impacts system security. The vulnerability occurs during the post-update task execution phase when the system temporarily grants unauthorized access to root's crontab file. This represents a time-based race condition where attackers can exploit a brief window of opportunity to gain sensitive information that would normally be restricted to privileged users. The flaw falls under CWE-362, which specifically addresses race conditions that can lead to security vulnerabilities, and aligns with ATT&CK technique T1059.007 for command and script injection.
The technical implementation of this vulnerability exploits the timing gap between when cPanel completes its update process and when it properly secures access to sensitive system files. During this transient period, the crontab file containing scheduled tasks with elevated privileges becomes accessible to unauthorized users. This creates a window where attackers can read root-level cron jobs that may contain sensitive credentials, system monitoring commands, or other privileged operations. The vulnerability demonstrates poor access control mechanisms and inadequate privilege management during system update procedures.
The operational impact of CVE-2018-20943 extends beyond simple information disclosure, as the crontab file often contains critical system maintenance commands, backup schedules, and potentially sensitive authentication tokens. Attackers who successfully exploit this vulnerability can gain intelligence about system administration practices, identify potential attack vectors, and potentially escalate privileges further by understanding how the system manages automated tasks. This information can be leveraged to plan more sophisticated attacks targeting the system's automated processes and scheduled maintenance windows.
Mitigation strategies for this vulnerability require immediate patching to cPanel version 68.0.27 or later, which addresses the race condition through improved access control mechanisms and proper privilege management during update processes. Organizations should implement comprehensive monitoring for unauthorized access attempts to system cron files and establish automated alerting for suspicious file access patterns. Additionally, system administrators should review and tighten access controls for cron-related files, implement proper file permissions, and conduct regular security audits to identify similar timing-based vulnerabilities in other system components. The fix demonstrates the importance of proper privilege separation and time-based access control in preventing race condition exploits that could lead to unauthorized system compromise.