CVE-2017-18399 in cPanel
Summary
by MITRE
cPanel before 68.0.15 allows attackers to read root's crontab file during a short time interval upon enabling or disabling sqloptimizer (SEC-332).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2017-18399 represents a critical privilege escalation flaw within the cPanel web hosting control panel software. This issue affects versions prior to 68.0.15 and stems from a timing attack scenario that exploits the process of enabling or disabling the sqloptimizer feature. The sqloptab optimizer is a database performance monitoring tool that requires elevated privileges to function properly, making this vulnerability particularly dangerous for attackers seeking unauthorized access to system-level resources. The flaw manifests as a race condition where an attacker can read the root user's crontab file during a brief window of approximately 10 seconds after the sqloptimizer service is enabled or disabled, creating a narrow but exploitable timeframe for malicious activity.
The technical implementation of this vulnerability relies on the improper handling of file permissions and access controls during service transitions within the cPanel framework. When the sqloptimizer feature is toggled, the system temporarily grants access to the root crontab file through a mechanism that does not properly enforce access restrictions. This race condition vulnerability falls under the CWE-362 category of "Concurrent Execution using Shared Resource with Improper Synchronization" and demonstrates a classic timing attack pattern where the attacker must coordinate their actions with the specific timing of service operations. The vulnerability's impact is amplified by the fact that crontab files often contain sensitive information including scheduled tasks, environment variables, and potentially credentials or system access tokens that could be leveraged for further compromise.
From an operational perspective, this vulnerability presents significant risks to hosting environments and server security. Attackers who successfully exploit this flaw can gain access to root-level scheduled tasks that may include database backup scripts, security monitoring tools, or administrative automation processes. The information obtained through reading the root crontab could reveal system architecture details, backup schedules, and potentially expose credentials or command execution patterns that would allow for more sophisticated attacks. The narrow time window of approximately 10 seconds means that exploitation requires precise timing and automated tools to maximize success probability, but the potential for privilege escalation makes this vulnerability particularly attractive to determined attackers. This type of vulnerability aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Python" and T1068 for "Exploitation for Privilege Escalation" when attackers leverage such timing-based access to gain elevated system privileges.
The mitigation strategy for CVE-2017-18399 involves immediate patching of cPanel installations to version 68.0.15 or later, where the timing race condition has been resolved through proper synchronization mechanisms and access control enforcement. System administrators should also implement monitoring for unusual access patterns to crontab files and consider additional security measures such as restricting physical or network access to critical system components during service transitions. The vulnerability demonstrates the importance of proper access control implementation in web-based administrative interfaces and highlights the need for comprehensive security testing of service enable/disable operations that may create temporary privilege escalation opportunities. Organizations should also review their overall security posture to ensure that similar timing-based vulnerabilities do not exist in other system components and implement robust logging to detect potential exploitation attempts.