CVE-2021-24347 in SP Project & Document Manager Plugin
Summary
by MITRE • 06/14/2021
The SP Project & Document Manager WordPress plugin before 4.22 allows users to upload files, however, the plugin attempts to prevent php and other similar files that could be executed on the server from being uploaded by checking the file extension. It was discovered that php files could still be uploaded by changing the file extension's case, for example, from "php" to "pHP".
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Analysis
by VulDB Data Team • 06/26/2024
The vulnerability identified as CVE-2021-24347 affects the SP Project & Document Manager WordPress plugin version 4.21 and earlier, representing a critical security flaw in file upload validation mechanisms. This issue stems from a flawed approach to file extension filtering that relies on case-sensitive comparison rather than comprehensive validation, creating a significant attack surface for malicious actors seeking to compromise WordPress installations. The vulnerability specifically targets the plugin's attempt to prevent execution of potentially harmful files such as php scripts, which could enable remote code execution and full system compromise. The flaw demonstrates a fundamental misunderstanding of secure file upload practices and highlights the importance of robust input validation in web applications.
The technical implementation of this vulnerability occurs through a simple yet effective bypass technique that exploits the plugin's inadequate validation logic. When the plugin processes file uploads, it performs extension checking but fails to implement proper case-insensitive comparison or comprehensive file type verification. Attackers can simply alter the case of file extensions from lowercase php to uppercase PHP or mixed case variations such as pHP, pHp, or PhP to circumvent the protection mechanism. This approach leverages the vulnerability described in CWE-174, which focuses on insufficient canonicalization of file paths and the failure to properly validate file attributes during upload processes. The flaw essentially represents a classic example of insecure input validation where the system assumes that case-sensitive checks provide sufficient protection against malicious file uploads.
The operational impact of CVE-2021-24347 extends far beyond simple file upload restrictions, potentially enabling attackers to achieve complete system compromise through remote code execution. Once a malicious php file is successfully uploaded despite the validation checks, it can be executed by the web server, allowing attackers to perform arbitrary code execution, access sensitive data, modify website content, or establish persistent backdoors. This vulnerability directly maps to the ATT&CK technique T1505.003 for Server Software Component, where adversaries leverage vulnerable software components to execute malicious code. The implications are particularly severe in WordPress environments where plugins often have elevated privileges and can access sensitive system resources. The vulnerability also aligns with ATT&CK technique T1078.004 for Valid Accounts, as compromised systems may allow attackers to maintain access through uploaded malicious scripts.
Mitigation strategies for CVE-2021-24347 must address both the immediate vulnerability and implement comprehensive secure file upload practices. The primary recommendation involves upgrading to plugin version 4.22 or later, which includes proper case-insensitive validation and enhanced file type checking mechanisms. Organizations should also implement multiple layers of defense including server-side file type verification using MIME type checking, content analysis, and file signature validation. Additional protective measures include restricting file upload capabilities to authenticated users only, implementing strict file naming conventions, and configuring web servers to prevent execution of uploaded files in web-accessible directories. The solution should incorporate the principles outlined in the OWASP Secure Coding Practices, specifically focusing on input validation and file handling security. System administrators should also consider implementing web application firewalls and intrusion detection systems to monitor for suspicious file upload activities. Regular security audits and vulnerability assessments should be conducted to identify similar implementation flaws in other plugins and custom code components that may present similar security risks.