CVE-2023-41108
📋 TL;DR
CVE-2023-41108 is an authenticated remote code execution vulnerability in TEF portal version 2023-07-17. Attackers with valid credentials can upload malicious files to execute arbitrary code on the server. This affects organizations using the vulnerable TEF portal software.
💻 Affected Systems
- TEF portal
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary commands, steal sensitive data, install malware, pivot to internal networks, and maintain persistent access.
Likely Case
Data exfiltration, installation of backdoors or ransomware, service disruption, and lateral movement within the network.
If Mitigated
Limited impact due to network segmentation, least privilege access, and proper monitoring detecting anomalous file uploads.
🎯 Exploit Status
Exploitation requires authenticated access but is straightforward once credentials are obtained. The CWE-434 (Unrestricted Upload of File with Dangerous Type) suggests file upload bypass techniques.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in references, but newer versions likely fix this
Vendor Advisory: https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2023-021.txt
Restart Required: Yes
Instructions:
1. Check vendor website for security updates. 2. Apply the latest patch for TEF portal. 3. Restart the application/service. 4. Verify the fix by testing file upload functionality.
🔧 Temporary Workarounds
Restrict File Upload Types
allConfigure the web server or application to only allow specific safe file types (e.g., .pdf, .jpg) and block executable extensions.
Implement Web Application Firewall Rules
allAdd WAF rules to block malicious file uploads and suspicious POST requests to upload endpoints.
🧯 If You Can't Patch
- Implement strict access controls and multi-factor authentication to limit authenticated access.
- Monitor and alert on unusual file upload activities and server-side command executions.
🔍 How to Verify
Check if Vulnerable:
Check if using TEF portal version 2023-07-17. Attempt to upload a file with dangerous extension while authenticated to see if it's blocked.Check Version:
Check application interface or configuration files for version information specific to TEF portal.Verify Fix Applied:
After patching, test file upload functionality with malicious file types to ensure they are rejected. Verify version is updated.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads with executable extensions
- POST requests to upload endpoints with suspicious filenames
- Server-side command execution logs
Network Indicators:
- HTTP POST requests to file upload endpoints with unusual payloads
- Outbound connections from the server to unknown IPs post-upload
SIEM Query:
source="web_server" AND (url_path="/upload" OR method="POST") AND (file_extension="exe" OR file_extension="php" OR file_extension="jsp")🔗 References
- https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2023-021.txt
- https://www.syss.de/pentest-blog/sicherheitsschwachstellen-im-tef-haendlerportal-syss-2023-020/-021
- https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2023-021.txt
- https://www.syss.de/pentest-blog/sicherheitsschwachstellen-im-tef-haendlerportal-syss-2023-020/-021
