Executive Summary

CVE-2026-4875 is an unrestricted file upload vulnerability in the Free Hotel Reservation System version 1.0, specifically in the file /admin/mod_amenities/index.php?view=add. The vulnerability occurs because the backend does not properly validate the file extensions or the actual content of uploaded files. This allows attackers to upload arbitrary files, including malicious PHP scripts disguised as images.

By exploiting this flaw, an attacker can upload and execute PHP code on the server remotely, leading to remote code execution (RCE). The vulnerability is facilitated by the exposure of the storage path of uploaded files and the lack of proper validation checks.

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Impact Analysis

This vulnerability can have severe impacts including full system compromise. An attacker can execute arbitrary commands on the server, steal or destroy sensitive data, deploy malware, and disrupt the hotel reservation services.

Because the attacker can upload and run malicious PHP scripts, they gain unauthorized control over the application and potentially the underlying server infrastructure, which can lead to significant operational and security risks.

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Detection Guidance

This vulnerability can be detected by monitoring for unauthorized or suspicious file uploads, especially PHP files disguised as images, to the endpoint `/admin/mod_amenities/controller.php?action=add`.

One way to detect exploitation attempts is to look for HTTP POST requests with multipart/form-data content type targeting this endpoint, containing files with suspicious extensions or content.

On the server, you can search for recently uploaded files with PHP extensions or files containing PHP code in the upload directory.

• Use web server logs to find POST requests to `/admin/mod_amenities/controller.php?action=add`.
• Run commands to find suspicious files, for example: `find /path/to/upload/directory -type f -name '*.php'`
• Check for PHP code inside files that should be images: `grep -r '<?php' /path/to/upload/directory`
• Use network monitoring tools to detect unusual POST requests uploading files to the vulnerable endpoint.

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Mitigation Strategies

Immediate mitigation steps include implementing strict validation and access controls on the file upload functionality.

• Implement a whitelist of allowed file extensions such as `.jpg`, `.png`, and `.gif` and reject all others on the server side.
• Validate the actual file content by checking file headers and magic bytes to ensure the uploaded file matches the declared type.
• Rename uploaded files with random filenames without user-supplied extensions and securely store the mapping.
• Restrict upload directory permissions to prevent execution of uploaded files and avoid placing uploads within the web root.
• Hide real storage paths from users by serving files through secure handler scripts.
• Enforce strong access controls to ensure only authorized administrators can access the upload functionality.

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Compliance Impact

The vulnerability allows attackers to upload and execute arbitrary files, including malicious scripts, leading to potential unauthorized access, data theft, and system compromise.

Such unauthorized access and potential data breaches can result in non-compliance with common standards and regulations like GDPR and HIPAA, which require protection of sensitive personal and health information.

Failure to remediate this vulnerability could lead to exposure of sensitive data, violating confidentiality and integrity requirements mandated by these regulations.

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