CVE-2023-25402
📋 TL;DR
CVE-2023-25402 is an unrestricted file upload vulnerability in CleverStupidDog yf-exam 1.8.0 that allows attackers to upload arbitrary files without suffix restrictions. This affects all users running yf-exam 1.8.0, potentially leading to remote code execution or system compromise.
💻 Affected Systems
- CleverStupidDog yf-exam
📦 What is this software?
Yf Exam by Yf Exam Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system takeover, data exfiltration, and lateral movement within the network.
Likely Case
Webshell upload enabling persistent backdoor access, data manipulation, and further exploitation of the server.
If Mitigated
Limited impact with proper file upload validation, web application firewalls, and restricted file permissions.
🎯 Exploit Status
Simple HTTP POST requests with malicious file uploads can exploit this vulnerability. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
No official patch available. Consider workarounds or alternative software.
🔧 Temporary Workarounds
Implement File Upload Validation
allAdd server-side validation to restrict allowed file types and extensions
Implement file type checking in upload handler code
Restrict uploads to specific whitelisted extensions
Web Application Firewall Rules
allBlock malicious file upload patterns at the WAF level
Add WAF rule to block uploads with dangerous extensions (.php, .jsp, .exe, etc.)
Implement file content inspection
🧯 If You Can't Patch
- Disable file upload functionality completely in yf-exam
- Isolate yf-exam instance in a restricted network segment with no internet access
🔍 How to Verify
Check if Vulnerable:
Attempt to upload a file with a malicious extension (.php, .jsp, .exe) to the yf-exam upload endpoint. If successful, system is vulnerable.Check Version:
Check yf-exam version in application configuration or about pageVerify Fix Applied:
Test file upload with restricted extensions. Malicious files should be rejected with proper error messages.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads with suspicious extensions
- Large number of upload requests
- Failed upload attempts with malicious extensions
Network Indicators:
- HTTP POST requests to upload endpoints with unusual file types
- Traffic spikes to upload functionality
SIEM Query:
source="web_server" AND (method="POST" AND uri="*upload*" AND (file_extension="php" OR file_extension="jsp" OR file_extension="exe"))