CVE-2005-4423 in PHPFM
Summary
by MITRE
Unrestricted file upload vulnerability in PHPFM before 0.2.3 allows remote authenticated users to execute arbitrary code by uploading a file with an executable extension to an accessible directory, as demonstrated using a file with a .php extension, aka "upload phpshell."
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Analysis
by VulDB Data Team • 10/01/2025
The vulnerability identified as CVE-2005-4423 represents a critical security flaw in PHPFM versions prior to 0.2.3 that enables authenticated remote attackers to achieve arbitrary code execution through unrestricted file upload capabilities. This vulnerability falls under the category of insecure file handling and demonstrates a fundamental weakness in input validation and access control mechanisms within the file management system. The flaw specifically allows attackers who have gained authentication credentials to upload malicious files to directories that are accessible via web requests, creating a direct pathway for code execution within the target environment.
The technical exploitation of this vulnerability relies on the absence of proper file extension validation and content verification mechanisms within PHPFM's upload functionality. When an authenticated user uploads a file with an executable extension such as .php, the system fails to properly validate the file type or content, allowing the uploaded file to be executed as PHP code by the web server. This creates a severe privilege escalation scenario where legitimate users can leverage their authenticated access to introduce malicious payloads that persist on the server and execute with the privileges of the web server process. The vulnerability is particularly dangerous because it requires only authentication credentials rather than exploiting additional system weaknesses, making it accessible to attackers who have already gained some level of access.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise. Attackers can upload various types of malicious files including web shells, backdoors, or other exploit payloads that provide persistent access to the compromised system. The vulnerability essentially transforms a legitimate file management function into a weapon for unauthorized system control, potentially allowing attackers to exfiltrate data, modify system files, or use the compromised server as a launch point for further attacks against internal networks. This type of vulnerability is classified under CWE-434 Unrestricted Upload of File with Dangerous Type, which specifically addresses the risks associated with allowing users to upload executable files without proper validation.
The attack vector for this vulnerability aligns with several techniques documented in the ATT&CK framework, particularly those related to initial access and execution phases. The requirement for authentication places this vulnerability in the context of credential compromise or insider threats, while the file upload mechanism maps to ATT&CK technique T1195.001 for Content Injection and T1059.007 for Command and Scripting Interpreter. The vulnerability demonstrates how seemingly benign functionality can be weaponized when proper security controls are absent, highlighting the importance of principle of least privilege and defense in depth strategies. Organizations with vulnerable PHPFM installations face significant risk of persistent threats, as the uploaded files remain executable until manually removed, providing attackers with long-term access to the compromised systems.
Mitigation strategies for CVE-2005-4423 require immediate implementation of proper file upload validation controls and access restrictions. The most effective approach involves implementing strict file type validation that rejects executable extensions and verifies file content against known signatures. Organizations should also implement proper directory permissions that prevent uploaded files from being executed by the web server, along with implementing secure upload directories that are separate from web-accessible locations. Additionally, the upgrade to PHPFM version 0.2.3 or later is essential as this release includes the necessary security patches to address the unrestricted file upload vulnerability. Network segmentation and monitoring for unusual file upload activities can also provide additional layers of defense against exploitation attempts.