CVE-2021-38611
📋 TL;DR
This CVE describes a command injection vulnerability in NASCENT RemKon Device Manager 4.0.0.0 that allows attackers to execute arbitrary commands with root privileges by uploading specially crafted filenames containing shell metacharacters. The vulnerability affects systems running the vulnerable version of the software, particularly those exposed to untrusted users who can access the image upload functionality.
💻 Affected Systems
- NASCENT RemKon Device Manager
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level access, allowing attackers to install malware, exfiltrate data, pivot to other systems, or render the system unusable.
Likely Case
Remote code execution leading to data theft, system modification, or deployment of ransomware/backdoors on vulnerable systems.
If Mitigated
Limited impact if proper network segmentation, input validation, and least privilege principles are implemented.
🎯 Exploit Status
The vulnerability is straightforward to exploit via web requests with shell metacharacters in filename parameters.
🛠️ 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
Web Application Firewall (WAF) Rules
allImplement WAF rules to block requests containing shell metacharacters in filename parameters.
WAF-specific configuration required
Input Validation Filter
linuxAdd server-side validation to reject filenames containing shell metacharacters before processing.
Modify assets/index.php to sanitize filename input
🧯 If You Can't Patch
- Isolate the vulnerable system in a restricted network segment with no internet access.
- Implement strict access controls to limit who can access the image upload functionality.
🔍 How to Verify
Check if Vulnerable:
Check if RemKon Device Manager version is 4.0.0.0 and if assets/index.php exists and processes image uploads without proper input validation.Check Version:
Check application version in web interface or configuration files.Verify Fix Applied:
Test uploading files with shell metacharacters in filenames; successful uploads should be rejected or sanitized.📡 Detection & Monitoring
Log Indicators:
- Web server logs showing POST requests to assets/index.php with unusual filenames containing characters like ;, |, &, $, (, ), `, or \n
Network Indicators:
- Unusual outbound connections from the RemKon server following image upload requests
SIEM Query:
source="web_server" AND uri="/assets/index.php" AND (filename="*;*" OR filename="*|*" OR filename="*&*" OR filename="*$*" OR filename="*(*" OR filename="*)*" OR filename="*`*" OR filename="*\\n*")🔗 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
