CVE-2024-40645 in FOG
Summary
by MITRE • 07/31/2024
FOG is a cloning/imaging/rescue suite/inventory management system. An improperly restricted file upload feature allows authenticated users to execute arbitrary code on the fogproject server. The Rebranding feature has a check on the client banner image requiring it to be 650 pixels wide and 120 pixels high. Apart from that, there are no checks on things like file extensions. This can be abused by appending a PHP webshell to the end of the image and changing the extension to anything the PHP web server will parse. This vulnerability is fixed in 1.5.10.41.
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Analysis
by VulDB Data Team • 09/06/2024
The FOG (Free Open-source Ghost) system represents a comprehensive network-based imaging solution designed for enterprise environments to manage computer deployments, system recovery, and inventory tracking. This vulnerability resides within the system's rebranding functionality, specifically targeting the client banner image upload mechanism that was intended to provide visual customization capabilities for organizations using the platform. The flaw manifests in the inadequate validation of uploaded files, creating a critical security gap that can be exploited by authenticated users with minimal privileges to gain full control over the underlying server infrastructure.
The technical implementation of this vulnerability stems from insufficient input validation within the file upload process. While the system does enforce dimensional constraints of 650 pixels wide by 120 pixels high for banner images, it completely neglects to validate file extensions, content types, or file signatures. This oversight creates a path for malicious actors to append PHP webshell code to legitimate image files and subsequently rename them with extensions that the PHP interpreter will process. The vulnerability essentially allows attackers to bypass the intended security boundaries by leveraging the legitimate upload functionality to introduce malicious code that executes within the context of the web server process. This represents a classic case of improper input validation and inadequate file type restrictions, which aligns with CWE-434 and CWE-20.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with complete server compromise capabilities. Once an attacker successfully uploads a malicious file, they can execute arbitrary commands with the privileges of the web server user, potentially leading to full system compromise, data exfiltration, or lateral movement within the network. The authenticated nature of the vulnerability means that attackers do not require privileged access to exploit this weakness, making it particularly dangerous in environments where multiple users have access to the FOG management interface. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1505.003 for Web Shell deployment and T1078.004 for Valid Accounts, as it leverages legitimate user credentials to perform malicious activities.
Organizations utilizing FOG systems should immediately implement mitigations including upgrading to version 1.5.10.41, which addresses this vulnerability through proper file extension validation and content type checking. Additional defensive measures should include implementing strict file upload restrictions that validate both file signatures and content, deploying web application firewalls to monitor for suspicious file upload patterns, and conducting regular security assessments of the system's file handling mechanisms. Network segmentation and privilege separation can also help limit the potential impact of successful exploitation, while comprehensive logging and monitoring of file upload activities can aid in detecting unauthorized attempts to exploit this vulnerability. The fix implemented in version 1.5.10.41 demonstrates proper security controls by enforcing comprehensive file validation that prevents the execution of potentially malicious code through the upload mechanism.