CVE-2020-22249 in PHPList
Summary
by MITRE • 07/07/2021
Remote Code Execution vulnerability in phplist 3.5.1. The application does not check any file extensions stored in the plugin zip file, Uploading a malicious plugin which contains the php files with extensions like PHP,phtml,php7 will be copied to the plugins directory which would lead to the remote code execution
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Analysis
by VulDB Data Team • 07/10/2021
The CVE-2020-22249 vulnerability represents a critical remote code execution flaw in phplist version 3.5.1 that stems from inadequate input validation during plugin installation processes. This vulnerability resides in the application's failure to properly validate file extensions within uploaded plugin zip archives, creating a pathway for malicious actors to execute arbitrary code on the target system. The flaw specifically affects the plugin management functionality where the system blindly copies files from uploaded zip archives to the plugins directory without performing extension checks or sanitization. This vulnerability directly maps to CWE-434 which describes insecure file upload vulnerabilities where applications fail to validate file types before processing them. The attack vector is particularly dangerous as it allows remote code execution through what appears to be a legitimate administrative function, making it difficult to detect and prevent through standard network monitoring.
The technical implementation of this vulnerability exploits the trust placed in the plugin installation mechanism within phplist. When administrators upload plugin zip files through the web interface, the application extracts all files contained within the archive and places them directly into the plugins directory structure. The vulnerability occurs because the application does not validate file extensions against a whitelist or perform proper sanitization of filenames during the extraction process. Malicious actors can craft zip files containing php files with extensions such as php, phtml, or php7 that would normally be rejected by the system but are instead copied to the plugins directory where they become executable. This behavior creates a persistent backdoor within the application's plugin architecture, allowing attackers to execute malicious code with the privileges of the web server process. The vulnerability operates at the application layer and can be exploited through unauthenticated access to the plugin upload functionality, making it particularly dangerous in environments where administrative access is not properly secured.
The operational impact of CVE-2020-22249 extends beyond simple code execution to encompass full system compromise and data exfiltration capabilities. Once successfully exploited, attackers can establish persistent access to the phplist installation, potentially leading to complete system takeover. The vulnerability enables attackers to deploy web shells, modify existing plugin functionality, or inject malicious code into the application's core processes. This compromise can result in unauthorized access to sensitive mailing list data, user information, and potentially serve as a foothold for broader network infiltration. The vulnerability also aligns with ATT&CK technique T1105 which describes remote file execution and can be leveraged as part of broader attack chains for lateral movement and privilege escalation. Organizations using phplist 3.5.1 are particularly vulnerable since the flaw exists in the core application logic rather than in third-party components, making traditional security controls less effective.
Mitigation strategies for CVE-2020-22249 require immediate action to address the root cause through proper input validation and file extension checking mechanisms. The primary recommendation involves implementing strict file extension validation that rejects any files with php-related extensions during plugin installation processes. Organizations should also implement proper file sanitization techniques that rename or strip potentially dangerous file extensions during the extraction process. Network segmentation and access controls should be enforced to limit administrative access to the plugin upload functionality, reducing the attack surface. Additionally, implementing web application firewalls with rules specifically designed to detect and block malicious file upload attempts can provide an additional layer of protection. Regular security audits and vulnerability assessments should be conducted to identify similar issues in other applications, particularly those with file upload capabilities. The vulnerability also highlights the importance of keeping applications updated and following secure coding practices, particularly around file handling and user input validation. Organizations should consider implementing automated patch management processes to ensure timely remediation of such vulnerabilities. This vulnerability serves as a reminder of the critical importance of proper file validation in web applications and aligns with security best practices outlined in OWASP Top Ten and NIST cybersecurity guidelines for preventing file upload vulnerabilities.