CVE-2025-6900: Library System RCE Vulnerability

CVE-2025-6900 Overview

A critical unrestricted file upload vulnerability has been identified in code-projects Library System version 1.0. The vulnerability exists in the /add-book.php file where the image parameter fails to properly validate uploaded files. This flaw allows remote authenticated attackers to upload arbitrary files to the server, potentially leading to remote code execution if malicious scripts are uploaded and subsequently executed.

Critical Impact
Attackers with low privileges can exploit this unrestricted file upload vulnerability to upload malicious files, potentially gaining remote code execution capabilities on the affected Library System server.

Affected Products

code-projects Library System version 1.0

Discovery Timeline

2025-06-30 - CVE-2025-6900 published to NVD
2025-07-01 - Last updated in NVD database

Technical Details for CVE-2025-6900

Vulnerability Analysis

This vulnerability is classified under CWE-434 (Unrestricted Upload of File with Dangerous Type) and CWE-284 (Improper Access Control). The /add-book.php endpoint in the Library System application accepts file uploads through the image parameter without implementing adequate file type validation or content verification. This oversight enables attackers to bypass intended restrictions and upload files with executable extensions or malicious content.

The attack can be initiated remotely by any authenticated user with access to the book addition functionality. The vulnerability has been publicly disclosed, and exploit details are available, increasing the risk of active exploitation against unpatched systems.

Root Cause

The root cause of this vulnerability stems from insufficient input validation on the file upload mechanism within /add-book.php. The application fails to implement proper checks for:

File extension validation against an allowlist
MIME type verification
Content-type header inspection
Magic byte validation to confirm actual file type

This lack of defense-in-depth allows attackers to manipulate the image parameter to upload files that should be restricted, such as PHP scripts or other executable content.

Attack Vector

The attack is network-based and requires low-privilege authentication to the Library System application. An attacker can craft a malicious request to the /add-book.php endpoint, submitting a dangerous file (such as a PHP webshell) through the image parameter. Upon successful upload, the attacker may then access the uploaded file directly through the web server to execute arbitrary code.

The vulnerability mechanism involves bypassing file type restrictions by manipulating either the filename extension, content-type header, or by exploiting the absence of server-side validation entirely. For technical details on the exploitation method, refer to the GitHub Issue CVE1 Report.

Detection Methods for CVE-2025-6900

Indicators of Compromise

Presence of unexpected file types (e.g., .php, .phtml, .jsp) in upload directories associated with the Library System
Web server logs showing POST requests to /add-book.php with unusual file extensions in the image parameter
Newly created executable files in web-accessible directories with recent timestamps
Unexpected outbound network connections originating from the web server process

Detection Strategies

Monitor file creation events in the Library System upload directories for executable file types
Implement web application firewall (WAF) rules to inspect and block requests containing executable file extensions in upload parameters
Review web server access logs for suspicious patterns targeting /add-book.php
Deploy file integrity monitoring on upload directories to detect unauthorized file additions

Monitoring Recommendations

Enable verbose logging for the /add-book.php endpoint to capture all upload attempts
Set up alerts for any file uploads that do not match expected image MIME types (e.g., image/jpeg, image/png, image/gif)
Monitor process execution on the web server for any processes spawned from upload directories
Implement network monitoring to detect potential command and control traffic if a webshell is deployed

How to Mitigate CVE-2025-6900

Immediate Actions Required

Restrict access to the /add-book.php functionality to only trusted administrative users
Implement strict file extension allowlisting (permit only .jpg, .jpeg, .png, .gif extensions)
Configure web server to prevent execution of scripts in upload directories
Review existing uploaded files for any malicious content and remove unauthorized files
Consider temporarily disabling the book addition feature until proper validation is implemented

Patch Information

As of the last update on 2025-07-01, no official vendor patch has been released for this vulnerability. System administrators should implement the recommended workarounds and monitor the Code Projects website for security updates. Additional technical details are available in the VulDB CTI Report #314392.

Workarounds

Implement server-side file type validation using magic byte inspection rather than relying on file extensions alone
Configure the web server to serve uploaded files with Content-Disposition: attachment headers to prevent direct execution
Move upload directories outside the web root and serve files through a controlled script
Apply strict permissions on upload directories to prevent script execution

bash

# Configuration example - Apache .htaccess for upload directory
# Place this file in the upload directory to prevent script execution

# Disable PHP execution in this directory
php_flag engine off

# Deny access to executable file types
<FilesMatch "\.(php|phtml|php3|php4|php5|pl|py|jsp|asp|aspx|cgi|sh)$">
    Require all denied
</FilesMatch>

# Force download instead of execution
<FilesMatch ".*">
    Header set Content-Disposition attachment
</FilesMatch>