CVE-2017-18390 in cPanel
Summary
by MITRE
cPanel before 68.0.15 allows code execution in the context of the root account because of weak permissions on incremental backups (SEC-322).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2017-18390 represents a critical privilege escalation flaw within cPanel software versions prior to 68.0.15. This issue stems from inadequate permission controls on incremental backup files, creating a pathway for malicious actors to execute arbitrary code with root-level privileges. The flaw specifically targets the backup functionality of cPanel, which is a widely deployed hosting control panel solution used by thousands of web hosting providers and system administrators worldwide. When incremental backups are created, they contain sensitive system data and configuration information that should remain protected from unauthorized access. The weak permissions allow local attackers with limited access to the system to manipulate backup files, potentially gaining elevated privileges and full system control.
The technical implementation of this vulnerability exploits the fundamental security principle of least privilege by failing to properly secure backup file permissions. Incremental backups in cPanel typically contain differential data that reflects changes since the last full backup, including configuration files, user data, and system settings. When these files are created with overly permissive access controls, they become vulnerable to manipulation by unauthorized users. The flaw enables attackers to modify backup files in such a way that when the backup system processes these files during restoration or maintenance operations, malicious code gets executed with root privileges. This represents a classic privilege escalation vulnerability where the attacker leverages a system component that should operate with elevated permissions to gain unauthorized access to the highest privilege level on the system.
The operational impact of CVE-2017-18390 extends far beyond simple code execution, as it provides complete system compromise capabilities for attackers who can access the target system. Once an attacker achieves root-level execution through this vulnerability, they can perform any action on the compromised system including installing malware, modifying system files, creating new user accounts, accessing all data, and potentially using the compromised system as a launch point for further attacks within a network infrastructure. The vulnerability is particularly dangerous because cPanel is commonly used in shared hosting environments where multiple users may have access to the system, making it easier for attackers to find and exploit this weakness. This flaw directly relates to CWE-276, which addresses incorrect permissions for critical resources, and aligns with ATT&CK techniques involving privilege escalation and persistence mechanisms.
Organizations affected by this vulnerability should immediately implement the remediation measures provided by cPanel in version 68.0.15 and subsequent releases. The fix involves strengthening the permission controls on incremental backup files to prevent unauthorized modification and execution. System administrators should also conduct comprehensive security audits to identify any potential exploitation attempts and ensure proper file permissions are maintained across all backup-related directories. Additional mitigations include implementing network segmentation to limit access to cPanel systems, monitoring for unusual backup file modifications, and conducting regular vulnerability assessments to identify similar permission-related flaws in other system components. The vulnerability demonstrates the critical importance of proper access control implementation in system components that handle sensitive data and configuration information, particularly those that operate with elevated privileges during normal operations.