CVE-2025-52376
📋 TL;DR
This authentication bypass vulnerability in Nexxt Solutions NCM-X1800 Mesh Router firmware allows attackers to remotely enable Telnet service without authentication, then access it with hard-coded credentials to gain administrative shell access. Attackers can execute arbitrary commands on compromised devices. All users of affected firmware versions are vulnerable.
💻 Affected Systems
- Nexxt Solutions NCM-X1800 Mesh Router
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to network takeover, data exfiltration, lateral movement to other devices, and persistent backdoor installation.
Likely Case
Router compromise allowing network traffic interception, DNS hijacking, credential theft, and botnet recruitment.
If Mitigated
Limited impact if device is behind firewall with strict inbound filtering and Telnet service disabled by default.
🎯 Exploit Status
Public exploit code available on GitHub. Simple HTTP request to vulnerable endpoint enables Telnet, then attacker uses hard-coded credentials.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Unknown
Restart Required: No
Instructions:
No official patch available. Check vendor website for firmware updates. If update available: 1. Download latest firmware from vendor site. 2. Log into router admin interface. 3. Navigate to firmware update section. 4. Upload and apply new firmware.
🔧 Temporary Workarounds
Block access to vulnerable endpoint
linuxUse firewall rules to block access to /web/um_open_telnet.cgi endpoint
iptables -A INPUT -p tcp --dport 80 -m string --string "/web/um_open_telnet.cgi" --algo bm -j DROP
Disable Telnet service permanently
allModify router configuration to disable Telnet service if possible
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict network segmentation
- Implement network monitoring for Telnet traffic (port 23) and block outbound Telnet connections
🔍 How to Verify
Check if Vulnerable:
Check if HTTP POST to http://[router-ip]/web/um_open_telnet.cgi with empty body returns success and enables Telnet on port 23Check Version:
Log into router web interface and check firmware version in System Status or About sectionVerify Fix Applied:
Attempt exploitation after applying workarounds - Telnet service should not be accessible on port 23📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /web/um_open_telnet.cgi
- Telnet service startup logs
- Failed/successful Telnet authentication attempts
Network Indicators:
- Unexpected Telnet traffic (TCP/23) to router
- HTTP requests to vulnerable endpoint from unusual sources
SIEM Query:
source="router_logs" AND (uri="/web/um_open_telnet.cgi" OR service="telnet")