CVE-2019-9825 in FeiFeiCms
Summary
by MITRE
FeiFeiCMS 4.1.190209 allows remote attackers to upload and execute arbitrary PHP code by visiting index.php?s=Admin-Index to modify the set of allowable file extensions, as demonstrated by adding php to the default jpg,gif,png,jpeg setting, and then using the "add article" feature.
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Analysis
by VulDB Data Team • 08/01/2023
FeiFeiCMS version 4.1.190209 contains a critical security vulnerability that allows remote attackers to execute arbitrary PHP code through a file upload functionality. This vulnerability stems from insufficient input validation and improper file extension handling within the administrative interface. The flaw specifically manifests when an attacker accesses the index.php?s=Admin-Index endpoint, which provides administrative controls for modifying the system's allowable file extensions. The vulnerability is classified under CWE-434, which addresses "Unrestricted Upload of File with Dangerous Type," representing a fundamental weakness in web application security where the application fails to properly validate file types before allowing uploads. The attack vector is particularly concerning as it leverages the legitimate administrative functionality of the content management system to bypass normal security controls.
The technical implementation of this vulnerability involves a configuration management flaw where the system maintains a default set of allowed file extensions including jpg, gif, png, and jpeg formats. Attackers can exploit this by modifying the extension whitelist to include php files, effectively creating a backdoor for code execution. Once the extension list is modified, the attacker can utilize the "add article" feature which processes file uploads through the vulnerable system. This process allows PHP code to be uploaded and subsequently executed within the web server context, providing attackers with full control over the affected system. The vulnerability demonstrates poor security design principles where administrative controls are not properly protected from unauthorized modification, enabling privilege escalation through simple parameter manipulation.
The operational impact of this vulnerability is severe and far-reaching for organizations using FeiFeiCMS 4.1.190209. Successful exploitation can lead to complete system compromise, data theft, service disruption, and potential lateral movement within network environments. Attackers can upload malicious PHP shells, web backdoors, or other malicious payloads that persist on the server and provide ongoing access. The vulnerability enables attackers to perform actions such as data exfiltration, privilege escalation, and establishing persistent access points within the network infrastructure. From an attack framework perspective, this vulnerability aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1078.004 for "Valid Accounts: Default Accounts" as it allows attackers to leverage legitimate administrative functions to achieve unauthorized code execution. The vulnerability also represents a critical weakness in the application's defense-in-depth strategy, as it bypasses multiple security layers including file type validation and administrative access controls.
Organizations should immediately implement multiple layers of mitigation to address this vulnerability. The primary recommendation involves patching the application to version 4.1.190210 or later, which contains the necessary security fixes. In the interim, administrators should restrict access to administrative endpoints through network segmentation, implementing strict firewall rules to limit access to the index.php?s=Admin-Index endpoint. Additionally, file upload validation should be strengthened by implementing strict file type checking, content validation, and ensuring that uploaded files are stored outside the web root directory. The system should also enforce proper authentication and authorization controls for administrative functions, including implementing multi-factor authentication and regular access reviews. Network monitoring should be enhanced to detect suspicious file upload activities and unusual administrative access patterns. Organizations should also conduct thorough security audits of their content management systems to identify similar vulnerabilities in other applications and ensure proper input validation across all file handling operations.