CVE-2018-20911 in cPanel
Summary
by MITRE
cPanel before 70.0.23 allows code execution because "." is in @INC during a Perl syntax check of cpaddonsup (SEC-359).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2018-20911 represents a critical code execution flaw within cPanel versions prior to 70.0.23, specifically affecting the Perl syntax checking mechanism used during cpaddonsup operations. This vulnerability stems from an insecure configuration where the current directory "." is included in the Perl INC array, which is a fundamental security risk in Perl-based environments. The INC array serves as Perl's module search path, and when the current directory is included without proper sanitization, it creates an opportunity for malicious code injection during syntax validation processes.
The technical exploitation occurs when the cpaddonsup utility performs a Perl syntax check on potentially untrusted input or modules. The presence of "." in @INC allows an attacker to place malicious Perl modules in the current working directory, which are then automatically loaded and executed during the syntax validation process. This creates a classic path traversal and code injection scenario where arbitrary Perl code can be executed with the privileges of the cPanel process. The vulnerability is particularly dangerous because it operates at the core of cPanel's administrative functionality, where cpaddonsup is responsible for managing addon domains and related configurations.
This flaw significantly impacts the operational security of affected systems by providing a direct path for remote code execution without requiring authentication or elevated privileges. The vulnerability can be exploited by attackers to gain unauthorized access to the system, potentially leading to complete compromise of the hosting environment. The attack vector is particularly concerning because it leverages legitimate cPanel functionality, making detection more difficult and allowing for persistent access. The vulnerability aligns with CWE-427 Uncontrolled Search Path Element, which specifically addresses insecure search path configurations that can lead to code injection attacks.
The operational impact extends beyond immediate code execution to encompass broader system compromise and data breach potential. Organizations running affected cPanel versions face significant risk of unauthorized access to customer data, website defacement, and potential lateral movement within network environments. The vulnerability affects hosting providers and their customers who rely on cPanel for web hosting management, creating cascading security implications for entire hosting ecosystems. Security professionals should consider this vulnerability in their ATT&CK framework analysis under T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation, as it provides both initial access and privilege escalation capabilities.
Mitigation strategies for CVE-2018-20911 require immediate patching of cPanel installations to version 70.0.23 or later, which addresses the insecure @INC configuration. System administrators should also implement additional security controls including restricting the execution of Perl scripts in sensitive directories, implementing proper input validation for cpaddonsup operations, and monitoring for suspicious file creation patterns in cPanel working directories. Network segmentation and access controls should be strengthened to limit potential attack surface, while regular security audits should verify that no malicious modules have been installed in the system. Organizations should also consider implementing automated patch management systems to ensure timely remediation of similar vulnerabilities in the future.