How to remediate – ZTE ZXV10 W300 Wireless Router Hard-coded Password

1. Introduction

The ZTE ZXV10 W300 Wireless Router contains a hard-coded password vulnerability. This means the device ships with pre-set credentials that are known to attackers, allowing unauthorised access. Businesses using this router model face a critical risk of full device control compromise. Successful exploitation could lead to data breaches, network disruption and loss of availability.

2. Technical Explanation

The ZTE ZXV10 W300 uses hard-coded credentials for the admin account. Nessus successfully logged in using a password derived from part of the device’s MAC address obtained via SNMP. Attackers can use this information to gain full administrative access without needing valid user credentials. This is documented under CVE-2014-0329.

• Root cause: The router uses predictable, hard-coded passwords for default accounts.
• Exploit mechanism: An attacker retrieves the MAC address using SNMP and constructs the password. They then use these credentials to log in via telnet or a web interface. For example, if the MAC address is 00:1A:2B:3C:4D:5E, the password could be prepended with this value.
• Scope: ZTE ZXV10 W300 Wireless Routers are affected. Specific firmware versions were not identified in the provided context.

3. Detection and Assessment

Confirming vulnerability requires checking for default credentials or identifying SNMP access. A quick check involves attempting login with known patterns, while thorough assessment uses a scanner.

• Quick checks: Attempt to log in via the web interface using common hard-coded password variations based on the device’s MAC address.
• Scanning: Nessus vulnerability ID 65310 can detect this issue. Other scanners may have similar signatures.
• Logs and evidence: Check router logs for successful logins from unexpected sources or failed login attempts with default credentials. The exact log location depends on the firmware version.

snmpwalk -v2c -c public <router_ip> ifDescr

4. Solution / Remediation Steps

There is no known patch for this vulnerability. The recommended workaround involves blocking SNMP and telnet access via firewall rules.

4.1 Preparation

• Dependencies: Access to the firewall or network device managing traffic to the ZTE ZXV10 W300. A change window may be necessary depending on your network environment.

4.2 Implementation

1. Step 1: Block incoming SNMP traffic (UDP port 161) to the router’s IP address.
2. Step 2: Block incoming telnet traffic (TCP port 23) to the router’s IP address.

4.3 Config or Code Example

Before

# No specific rules blocking SNMP or Telnet (example Cisco IOS)
!

After

# Block incoming SNMP and telnet traffic (example Cisco IOS)
access-list 10 deny udp any host <router_ip> eq snmp
access-list 10 deny tcp any host <router_ip> eq telnet
!

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help mitigate this type of vulnerability.

• Practice 1: Least privilege – limit access to devices and accounts only to those who need it, reducing the impact if compromised.
• Practice 2: Secure defaults – change all default passwords immediately upon deployment.

4.5 Automation (Optional)

If using infrastructure-as-code, firewall rules can be automated.

# Example Ansible playbook snippet to block SNMP and Telnet
- name: Block SNMP and Telnet traffic
  firewalld:
    port: "{{ item.port }}/{{ item.protocol }}"
    permanent: true
    state: disabled
  loop:
    - { port: 161, protocol: udp }
    - { port: 23, protocol: tcp }
  become: true

5. Verification / Validation

Confirm the fix by verifying blocked traffic and re-running the initial detection method.

• Post-fix check: Use `tcpdump` or similar to confirm that SNMP and telnet packets are being dropped at the firewall.
• Re-test: Re-run the Nessus scan (ID 65310) to ensure it no longer detects the vulnerability.
• Smoke test: Verify basic internet connectivity from devices behind the router is still functioning.
• Monitoring: Monitor firewall logs for blocked SNMP and telnet attempts as an indicator of potential attacks.

tcpdump -i eth0 port 161 or port 23

6. Preventive Measures and Monitoring

Proactive security measures can prevent similar vulnerabilities.

• Baselines: Update your network device baseline to include requirements for strong passwords and disabling unnecessary services like SNMP and telnet.
• Asset and patch process: Establish a regular review cycle for security advisories and apply patches promptly, where available.

7. Risks, Side Effects, and Roll Back

Blocking SNMP may impact network management tools that rely on it.

• Risk or side effect 1: Blocking SNMP could disrupt network monitoring systems if they use the default community string. Mitigate by reconfiguring monitoring to use secure alternatives.
• Roll back: Remove the firewall rules created in Step 4.2 to restore SNMP and telnet access.

8. References and Resources

Links to official advisories related to this vulnerability.

• Vendor advisory or bulletin: http://www.nessus.org/u?aad205ef
• NVD or CVE entry: CVE-2014-0329
• Product or platform documentation relevant to the fix: https://www.kb.cert.org/vuls/id/228886/