CVE-2018-20947 in cPanel
Summary
by MITRE
cPanel before 68.0.27 allows certain file-write operations via the telnetcrt script (SEC-356).
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Analysis
by VulDB Data Team • 07/18/2020
The vulnerability identified as CVE-2018-20947 affects cPanel versions prior to 68.0.27 and represents a critical file write privilege escalation flaw within the telnetcrt script. This vulnerability falls under the category of insecure direct object reference and improper access control as classified by CWE-284, where the telnetcrt script fails to properly validate user inputs and lacks adequate permission checks before executing file operations. The telnetcrt script is designed to handle terminal emulation and connection management within the cPanel environment, but due to insufficient sanitization of input parameters, malicious actors can manipulate file paths and execute unauthorized write operations.
The technical exploitation of this vulnerability occurs when an attacker can manipulate the parameters passed to the telnetcrt script, potentially allowing them to write arbitrary files to the filesystem with elevated privileges. This flaw stems from the script's improper handling of user-supplied data, particularly when processing terminal connection requests that may include file path specifications. The vulnerability is particularly concerning because it operates within the cPanel administrative interface, which typically requires elevated privileges, yet the script does not properly enforce access controls or validate the legitimacy of file operations being requested. The flaw enables an attacker to potentially overwrite critical system files, create backdoor accounts, or modify configuration files that could lead to complete system compromise.
From an operational standpoint, this vulnerability presents a significant risk to web hosting environments that rely on cPanel for server management. Attackers who can exploit this issue gain the ability to perform unauthorized file modifications, which could result in data corruption, system instability, or complete takeover of the hosting environment. The impact extends beyond individual server compromise as cPanel instances often manage multiple customer accounts, making this vulnerability a potential vector for widespread damage. Organizations using affected cPanel versions face immediate risk of unauthorized access, data breaches, and potential regulatory violations, particularly in environments where compliance with standards like pci dss or hipaa is required. The vulnerability aligns with attack patterns documented in the mitre att&ck framework under initial access and privilege escalation techniques, specifically targeting the execution of malicious code through legitimate system tools.
The recommended mitigation strategy involves immediately upgrading to cPanel version 68.0.27 or later, which includes proper input validation and access control mechanisms for the telnetcrt script. System administrators should also implement network segmentation and restrict access to cPanel administrative interfaces to trusted networks only. Additional protective measures include monitoring for unusual file modification patterns, implementing intrusion detection systems, and conducting regular security audits of web hosting environments. Organizations should also consider implementing application whitelisting policies and ensuring that all system components are regularly updated to address known vulnerabilities. The fix implemented in version 68.0.27 addresses the root cause by introducing proper parameter validation and access control checks that prevent unauthorized file write operations while maintaining legitimate functionality of the telnetcrt script.