Critical Vulnerability Information Vulnerability Description Type: Arbitrary File Upload Vulnerability Impact: Allows attackers to upload malicious PHP scripts, bypassing file type and content validation, leading to remote code execution, sensitive data leakage, privilege escalation, and lateral movement. Affected Product Product Name: Library System Affected Version: V1.0 Download Link: Library System PHP with Source Code Technical Details Root Cause: - Inadequate independent file upload validation. - No restriction on file extensions (e.g., ). - Insufficient MIME type validation (e.g., can be spoofed as ). - Lack of signature validation (e.g., AntSword PHP script signature). Upload Path Access: Uploaded files stored in accessible directories (e.g., ), with no execution permission restrictions. Attack Vector 1. Upload a PHP webshell via AntSword using a POST request. 2. Connect to the webshell using the AntSword client and send system commands. 3. Execute remote commands: retrieve system information and file listings. POC (Proof of Concept) 1. Example POST Request to Upload AntSword Webshell 2. Example AntSword Connection Impact Full system control: execution of arbitrary system commands. Sensitive data leakage: access to database configurations, source code, and user information. Privilege escalation and lateral movement: exploit server file upload functionality for privilege escalation or lateral movement. Malware persistence: upload additional backdoors to maintain long-term control over the system. Mitigation Measures Immediate Fixes: 1. Block malicious script uploads: 2. Add WAF rules to block requests containing , , or parameters. Long-term Solutions: 1. Strengthen file upload validation: - Use a whitelist for allowed formats (e.g., JPEG). - Check file headers to confirm file type. - Rename uploaded files with random names. 2. Restrict directory execution permissions: - Set directories to non-executable. 3. Monitor suspicious requests: - Log requests containing dangerous functions. - Use ELK stack to monitor suspicious activities in web directories.