CVE-2018-20909 in cPanel
Summary
by MITRE
cPanel before 70.0.23 allows arbitrary file-chmod operations during legacy incremental backups (SEC-338).
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Analysis
by VulDB Data Team • 07/18/2020
This vulnerability exists within cPanel versions prior to 70.0.23 and represents a critical security flaw that enables unauthorized file permission modifications during legacy incremental backup operations. The issue stems from insufficient input validation and access control mechanisms that allow malicious actors to manipulate file permissions on the system. When cPanel processes legacy incremental backups, it fails to properly validate the file paths and permission changes being requested, creating an avenue for arbitrary chmod operations that can compromise system integrity and security posture.
The technical implementation of this vulnerability occurs within the backup processing module where legacy incremental backup functionality is handled. Attackers can exploit this weakness by crafting specific backup requests that include malicious file path specifications or permission values that would normally require administrative privileges to modify. This flaw operates at the system level where file permissions are manipulated without proper authentication or authorization checks, allowing attackers to elevate their privileges or disrupt normal system operations. The vulnerability specifically affects the backup restoration and update processes where file permissions are automatically adjusted based on backup data.
The operational impact of CVE-2018-20909 extends beyond simple permission modifications and can lead to severe system compromise. An attacker who successfully exploits this vulnerability can potentially make critical system files executable, modify configuration files, or create backdoor access points within the system. This arbitrary chmod capability can be leveraged to escalate privileges, disable security controls, or establish persistent access to the compromised system. The vulnerability affects both the integrity and availability of the system as unauthorized modifications can render critical components unusable or compromise their security properties.
Organizations affected by this vulnerability should immediately update to cPanel version 70.0.23 or later to remediate the issue. The patch addresses the core validation flaw in the backup processing module and implements proper access control checks for file permission modifications. Security administrators should also conduct thorough audits of backup operations and file permissions to identify any unauthorized changes that may have occurred during the vulnerability window. Additional mitigations include implementing network segmentation around cPanel systems, monitoring backup operations for unusual permission changes, and ensuring proper file system permissions are maintained through regular security assessments. This vulnerability aligns with CWE-276 which addresses improper file permissions and can be mapped to ATT&CK technique T1074 for data staging and T1486 for data encryption for ransomware attacks that could leverage such permission manipulation capabilities.
The broader implications of this vulnerability highlight the critical importance of proper input validation and access control in backup and restore operations. Legacy systems often contain security gaps that become apparent when modern attack vectors are applied against them, making regular security updates and comprehensive vulnerability assessments essential. Organizations should implement automated patch management processes specifically targeting web hosting control panels and ensure that backup operations are monitored for suspicious activities that could indicate exploitation attempts. The vulnerability demonstrates how seemingly routine system operations can become attack vectors when proper security controls are absent from legacy code implementations.