CVE-2020-20979 in LJCMS
Summary
by MITRE • 08/12/2021
An arbitrary file upload vulnerability in the move_uploaded_file() function of LJCMS v4.3 allows attackers to execute arbitrary code.
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Analysis
by VulDB Data Team • 06/20/2023
The CVE-2020-20979 vulnerability represents a critical arbitrary file upload flaw within LJCMS v4.3 that directly leverages the move_uploaded_file() function to enable remote code execution. This vulnerability exists due to insufficient input validation and sanitization mechanisms within the content management system's file upload handling logic. The flaw allows attackers to bypass security restrictions and upload malicious files that can subsequently be executed on the target server, creating a severe attack surface that can be exploited for complete system compromise.
From a technical perspective, the vulnerability stems from the improper validation of file extensions and content types during the upload process. The move_uploaded_file() function in php is designed to move uploaded files from temporary storage to their final destination, but in LJCMS v4.3, this function operates without adequate checks to verify that uploaded files conform to expected security parameters. Attackers can manipulate the upload process to bypass file type restrictions, potentially uploading web shells or other malicious executables that execute with the privileges of the web server process. This weakness aligns with CWE-434 which specifically addresses insecure file upload vulnerabilities where applications fail to properly validate uploaded files.
The operational impact of this vulnerability is severe and multifaceted, as it directly enables attackers to achieve persistent access to the affected system. Once exploited, an attacker can upload malicious files that provide remote code execution capabilities, allowing for data exfiltration, system reconnaissance, and potential lateral movement within the network. The vulnerability can be exploited through various attack vectors including web application interfaces, API endpoints, or file upload forms that utilize the vulnerable move_uploaded_file() function. According to ATT&CK framework, this vulnerability maps to T1190 (Exploit Public-Facing Application) and T1059 (Command and Scripting Interpreter) techniques, demonstrating how attackers can leverage the vulnerability to establish persistent access and execute commands on the compromised system.
Mitigation strategies for CVE-2020-20979 should focus on implementing robust input validation, file type restrictions, and proper file handling mechanisms. Organizations should immediately upgrade to the latest version of LJCMS where this vulnerability has been patched, as the vendor has likely addressed the insecure file upload logic. Additional defensive measures include implementing strict file extension validation, using randomized filenames for uploaded content, implementing proper access controls for uploaded files, and deploying web application firewalls that can detect and block malicious upload attempts. Security monitoring should be enhanced to detect unusual file upload patterns, and regular security assessments should be conducted to identify similar vulnerabilities in other applications and systems. The vulnerability also underscores the importance of following secure coding practices and implementing proper sanitization of user inputs as recommended by OWASP Top Ten security guidelines.