CVE-2021-38613
📋 TL;DR
This vulnerability allows attackers to upload arbitrary code through the Image Upload feature in NASCENT RemKon Device Manager, leading to remote code execution. It affects systems running RemKon Device Manager 4.0.0.0 with the vulnerable assets/index.php component exposed.
💻 Affected Systems
- NASCENT RemKon Device Manager
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the target system, potentially leading to data theft, lateral movement, or ransomware deployment.
Likely Case
Attackers upload web shells or malicious scripts to execute commands, steal credentials, or deploy malware on vulnerable systems.
If Mitigated
Limited impact with proper file upload validation and execution restrictions in place.
🎯 Exploit Status
Exploitation requires only web access to the vulnerable endpoint. Public technical details available from security researchers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.nascent.com/single-post/2019/01/17/nascent-technology-releases-remkon-31-to-enhance-audio-experience
Restart Required: No
Instructions:
No official patch available. Consider upgrading to newer versions if available, or implement workarounds.
🔧 Temporary Workarounds
Restrict access to assets/index.php
allBlock or restrict access to the vulnerable upload endpoint using web server configuration or firewall rules.
# Apache: Add to .htaccess
<Files "assets/index.php">
Order Deny,Allow
Deny from all
</Files>
# Nginx: Add to server block
location ~ /assets/index\.php$ {
deny all;
return 403;
}
Implement file upload validation
allAdd server-side validation to restrict uploaded files to specific image types only.
# Example PHP validation snippet
$allowed_types = ['image/jpeg', 'image/png', 'image/gif'];
if (!in_array($_FILES['file']['type'], $allowed_types)) {
die('Invalid file type');
}
🧯 If You Can't Patch
- Isolate vulnerable systems from internet and restrict network access
- Implement strict file upload validation and disable execution in upload directories
🔍 How to Verify
Check if Vulnerable:
Check if assets/index.php exists and accepts file uploads without proper validation. Test by attempting to upload a non-image file.Check Version:
Check RemKon Device Manager version in web interface or configuration filesVerify Fix Applied:
Verify that file uploads are properly restricted to image types only and that uploaded files cannot be executed.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads to assets/index.php
- Execution of uploaded files from upload directories
- Web server errors related to file type validation
Network Indicators:
- HTTP POST requests to /assets/index.php with file uploads
- Subsequent requests to uploaded files in upload directories
SIEM Query:
source="web_server" AND (uri="/assets/index.php" AND method="POST") AND (file_extension!=".jpg" AND file_extension!=".png" AND file_extension!=".gif")🔗 References
- https://www.blacklanternsecurity.com/2021-08-23-Nascent-RemKon-CVEs/
- https://www.nascent.com/single-post/2019/01/17/nascent-technology-releases-remkon-31-to-enhance-audio-experience
- https://www.blacklanternsecurity.com/2021-08-23-Nascent-RemKon-CVEs/
- https://www.nascent.com/single-post/2019/01/17/nascent-technology-releases-remkon-31-to-enhance-audio-experience
