CVE-2018-17836 in JTBC(PHP)
Summary
by MITRE
An issue was discovered in JTBC(PHP) 3.0.1.6. It allows remote attackers to execute arbitrary PHP code by using a /console/file/manage.php?type=action&action=addfile&path=..%2F substring to upload, in conjunction with a multipart/form-data PHP payload.
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Analysis
by VulDB Data Team • 03/28/2020
The vulnerability identified as CVE-2018-17836 resides within JTBC(PHP) version 3.0.1.6, representing a critical remote code execution flaw that enables attackers to gain unauthorized control over affected systems. This vulnerability stems from inadequate input validation and improper file handling mechanisms within the console file management component of the application. The flaw specifically manifests when attackers exploit the /console/file/manage.php endpoint with crafted parameters that manipulate the file upload process.
The technical implementation of this vulnerability leverages a combination of path traversal techniques and malicious file upload capabilities. Attackers can construct malicious requests using the type=action&action=addfile&path=..%2F parameter sequence which effectively bypasses directory restrictions and allows arbitrary file placement within the application's directory structure. The path traversal component utilizes the ..%2F encoding to navigate upward in the directory hierarchy, while the multipart/form-data payload contains PHP code that gets executed when the uploaded file is accessed. This combination creates a persistent backdoor within the web application's file system.
The operational impact of CVE-2018-17836 extends beyond simple code execution, as it provides attackers with complete system compromise capabilities. Once successful, attackers can establish persistent access, escalate privileges, exfiltrate sensitive data, and potentially use the compromised system as a launching point for further attacks within the network. The vulnerability affects the application's integrity and confidentiality, making it particularly dangerous for environments where JTBC(PHP) is deployed. The attack vector requires no authentication, making it especially severe as it can be exploited by anyone with access to the affected web application.
Security professionals should recognize this vulnerability as a variant of CWE-434, which deals with Unrestricted Upload of File with Dangerous Type, and aligns with ATT&CK techniques related to Command and Control and Execution. The flaw demonstrates poor input sanitization practices and inadequate access controls within the file management system. Organizations should immediately implement mitigations including restricting file upload capabilities, implementing strict file type validation, and deploying web application firewalls to detect and block malicious upload attempts. Additionally, regular security audits and penetration testing should be conducted to identify similar vulnerabilities in other components of the application stack. The vulnerability highlights the importance of proper secure coding practices and the necessity of validating all user inputs to prevent path traversal attacks and unauthorized code execution.