CVE-2025-4538
📋 TL;DR
CVE-2025-4538 is a critical unrestricted file upload vulnerability in kkFileView 4.4.0 that allows remote attackers to upload arbitrary files to the /fileUpload endpoint. This affects all systems running the vulnerable version of kkFileView, potentially enabling server compromise.
💻 Affected Systems
- kkFileView
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data exfiltration, and lateral movement within the network.
Likely Case
Webshell deployment allowing persistent access, file system manipulation, and potential privilege escalation.
If Mitigated
File upload attempts are blocked or quarantined, preventing successful exploitation.
🎯 Exploit Status
Exploit details are publicly available, making weaponization likely. No authentication required for exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None available
Restart Required: No
Instructions:
No official patch available. Vendor was contacted but did not respond. Consider upgrading to a newer version if available or implementing workarounds.
🔧 Temporary Workarounds
Web Application Firewall Rules
allImplement WAF rules to block malicious file uploads to /fileUpload endpoint
File Upload Restrictions
linuxConfigure web server to restrict file types and sizes for uploads
# Example nginx restriction
location /fileUpload {
client_max_body_size 1M;
deny all;
}
🧯 If You Can't Patch
- Disable or block access to the /fileUpload endpoint entirely
- Implement strict file type validation and scanning for all uploads
🔍 How to Verify
Check if Vulnerable:
Check if kkFileView version is 4.4.0 and /fileUpload endpoint is accessibleCheck Version:
Check application configuration or deployment files for version informationVerify Fix Applied:
Test file upload functionality with restricted file types and verify uploads are properly validated📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads to /fileUpload
- Uploads of executable file types
- Multiple failed upload attempts
Network Indicators:
- POST requests to /fileUpload with suspicious file extensions
- Unusual outbound connections after uploads
SIEM Query:
source="web_logs" AND uri="/fileUpload" AND (file_extension="php" OR file_extension="jsp" OR file_extension="asp")🔗 References
- https://magnificent-dill-351.notion.site/Arbitrary-File-Upload-in-kkFileView-4-4-0-1e3c693918ed802581faccab9140a130
- https://vuldb.com/?ctiid.308283
- https://vuldb.com/?id.308283
- https://vuldb.com/?submit.566596
- https://magnificent-dill-351.notion.site/Arbitrary-File-Upload-in-kkFileView-4-4-0-1e3c693918ed802581faccab9140a130
