CVE-2018-20942 in cPanel
Summary
by MITRE
cPanel before 68.0.27 allows attackers to read root's crontab file during a short time interval upon configuring crontab (SEC-351).
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Analysis
by VulDB Data Team • 07/18/2020
This vulnerability exists in cPanel versions prior to 68.0.27 and represents a critical privilege escalation issue that allows unauthenticated attackers to access root's crontab file during a specific time window. The flaw occurs during the crontab configuration process when the system temporarily exposes sensitive administrative information. This vulnerability falls under the category of insecure direct object reference and privilege escalation as outlined in CWE-284 and CWE-269 respectively. The attack vector leverages the timing window between when crontab configuration begins and when proper access controls are enforced, creating a brief window of opportunity for unauthorized information disclosure.
The technical implementation of this vulnerability stems from improper access control mechanisms during crontab processing. When system administrators configure crontab entries, the underlying system temporarily grants elevated privileges to certain processes that handle the configuration. During this brief interval, the root crontab file becomes accessible to unauthorized users without proper authentication. This timing-based vulnerability is particularly dangerous because it exploits the window of opportunity between process initialization and privilege enforcement, making it difficult to detect and prevent through traditional monitoring approaches. The vulnerability is classified as a time-of-check to time-of-use issue that aligns with ATT&CK technique T1059.007 for command and script interpretation.
The operational impact of this vulnerability extends beyond simple information disclosure, as crontab files often contain sensitive system automation tasks, backup schedules, and administrative commands that could provide attackers with insights into system architecture and potential attack vectors. An attacker could potentially discover scheduled maintenance tasks, database backup routines, or other administrative processes that might reveal system dependencies or weaknesses. The vulnerability affects the integrity and confidentiality of system administration functions, potentially enabling more sophisticated attacks including privilege escalation to full system compromise. Organizations running vulnerable cPanel versions face significant risk of unauthorized access to critical system information that could be used for further exploitation or lateral movement within their infrastructure.
Mitigation strategies should focus on immediate patching to cPanel version 68.0.27 or later, which addresses the timing window issue through improved access control enforcement. System administrators should implement comprehensive monitoring of crontab-related activities and establish automated alerts for any unauthorized access attempts. Network segmentation and access control policies should be reviewed to minimize the attack surface, particularly around administrative interfaces. Additionally, organizations should conduct regular vulnerability assessments targeting web-based administration interfaces and implement principle of least privilege controls for all administrative functions. The remediation process should include verification of crontab file permissions and access logs to ensure no unauthorized access occurred during the vulnerable period, with particular attention to the timing of administrative activities that could have exposed sensitive information.