CVE-2025-67288
📋 TL;DR
An arbitrary file upload vulnerability in Umbraco CMS v16.3.3 allows attackers to upload malicious PDF files that can lead to remote code execution. This affects administrators who have not implemented proper file validation controls. The vendor disputes this as a vulnerability, stating file validation responsibility lies with system administrators implementing Umbraco.
💻 Affected Systems
- Umbraco CMS
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the web server, data exfiltration, and lateral movement within the network.
Likely Case
Webshell deployment leading to data theft, defacement, or use as a foothold for further attacks.
If Mitigated
No impact if proper file type validation and upload restrictions are implemented.
🎯 Exploit Status
Exploit requires access to file upload functionality. Public proof-of-concept exists in GitHub repository.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: http://umbraco.com
Restart Required: No
Instructions:
No official patch available as vendor disputes this as a vulnerability. Implement file validation controls as described in Umbraco documentation.
🔧 Temporary Workarounds
Implement File Type Validation
allRestrict uploaded files to specific allowed types and validate file signatures
Upload Directory Restrictions
allConfigure upload directories to prevent execution of uploaded files
🧯 If You Can't Patch
- Disable file upload functionality entirely if not required
- Implement web application firewall rules to block malicious file uploads
🔍 How to Verify
Check if Vulnerable:
Check if Umbraco version is 16.3.3 and file upload functionality exists without proper validation controls.Check Version:
Check Umbraco version in administration panel or web.config fileVerify Fix Applied:
Test file upload functionality with malicious PDF files to ensure they are rejected.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads, particularly PDF files with unusual sizes or names
- Webshell creation in upload directories
Network Indicators:
- HTTP POST requests with file uploads containing executable code patterns
SIEM Query:
source="web_server" AND (method="POST" AND uri="*/upload*" AND file_extension="pdf")