How to remediate – Grandstream Phone Web Interface Default Credentials

1. Introduction

The Grandstream Phone Web Interface Default Credentials vulnerability allows unauthenticated access to a device’s web interface due to the use of default login credentials. This poses a risk to business confidentiality, integrity and availability as attackers can gain full control over affected phones. These vulnerabilities typically affect Grandstream phone models with exposed web interfaces. A successful exploit could lead to complete system compromise, including eavesdropping, call manipulation, and denial of service.

2. Technical Explanation

The vulnerability stems from the use of hardcoded default credentials (often username ‘admin’ and password ‘admin’) on Grandstream phone web interfaces. Attackers can remotely access these interfaces without authentication if the default credentials have not been changed. There is no known CVE associated with this specific issue, but it falls under CWE-798: Use of Hard-coded Credentials. An attacker could use a simple HTTP request to access the interface and then log in using the default credentials. Affected devices include Grandstream phones running firmware where default credentials are enabled.

• Root cause: The remote device uses default, well-known credentials for web interface access.
• Exploit mechanism: An attacker attempts to login to the web interface with default username and password.
• Scope: Grandstream phones with a web interface enabled and using default credentials.

3. Detection and Assessment

You can confirm if a system is vulnerable by checking for the presence of the default credentials or an exposed web interface. A quick check involves attempting to access the web interface with default login details. More thorough assessment includes scanning for open ports and banner grabbing.

• Quick checks: Attempt to log in to the phone’s web interface using username ‘admin’ and password ‘admin’.
• Scanning: Nessus plugin ID 10389 can identify Grandstream phones with default credentials, but results should be verified manually.
• Logs and evidence: Check firewall logs for connections to port 80 or 443 originating from external sources attempting to access the phone’s web interface.

ping {phone_ip}

4. Solution / Remediation Steps

The solution is to replace the default password with a strong, unique password. Follow these steps carefully to avoid service disruption.

4.1 Preparation

• No services need to be stopped for this process.
• A roll back plan involves restoring the backed-up configuration if necessary.

4.2 Implementation

1. Step 1: Access the Grandstream phone’s web interface using a web browser.
2. Step 2: Log in with the default credentials (username ‘admin’, password ‘admin’).
3. Step 3: Navigate to the “System” or “Administration” section of the web interface.
4. Step 4: Locate the “Change Password” option and enter a new, strong password.
5. Step 5: Save the changes and log out of the web interface.

4.3 Config or Code Example

Before

Username: admin
Password: admin

After

Username: admin
Password: {strong_password} 

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this issue. Least privilege reduces the impact of a compromised account. Safe defaults ensure systems are not initially exposed with weak credentials. Regular patch cadence ensures known vulnerabilities are addressed promptly.

• Practice 1: Implement least privilege to limit access rights and reduce potential damage from compromised accounts.
• Practice 2: Enforce strong password policies, including complexity requirements and regular changes.

4.5 Automation (Optional)

Automation is not generally suitable for this vulnerability due to the device-specific nature of web interface access.

5. Verification / Validation

• Post-fix check: Attempt to log in using username ‘admin’ and the *old* password – it should fail.
• Re-test: Repeat step 2 from section 3, attempting login with default credentials; access should be denied.
• Smoke test: Make a test call through the phone to confirm basic calling functionality is working as expected.

Attempt login via web interface using admin/admin - Access Denied

6. Preventive Measures and Monitoring

Update security baselines to include strong password requirements for all network devices. Implement CI/CD pipeline checks to ensure default credentials are not present in configuration files. Establish a regular patch or config review cycle to identify and address vulnerabilities promptly.

• Baselines: Update your security baseline to require strong passwords on all Grandstream phones.
• Pipelines: Include static analysis of configuration files to detect the presence of default credentials.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Incorrectly entered new password may result in loss of access.
• Roll back: Restore the phone’s configuration from the backup created in section 4.1.

8. References and Resources

Links to official advisories and trusted documentation related to this vulnerability.

• Vendor advisory or bulletin: Grandstream Security Advisories
• NVD or CVE entry: No specific CVE exists for default credentials, but search for Grandstream vulnerabilities on the NVD website (https://nvd.nist.gov/).