How to remediate – UPnP Internet Gateway Device (IGD) Protocol Detection

1. Introduction

The UPnP Internet Gateway Device (IGD) Protocol Detection vulnerability means a device supports the IGD protocol, which is used by NAT routers. This can allow attackers on the same network to bypass firewall protections using techniques like malicious Flash animations or JavaScript. Businesses are at risk if these devices are exposed to untrusted networks. Confidentiality, integrity and availability may be compromised if an attacker gains access to internal systems.

2. Technical Explanation

The IGD protocol allows applications to control NAT routers. The vulnerability arises because the protocol can allow external access to services behind a firewall without explicit configuration. An attacker could exploit this by sending commands to the router, opening ports and redirecting traffic. This requires the target device to have UPnP enabled and be accessible from the network.

• Root cause: The IGD protocol allows remote control of NAT functions with insufficient security checks.
• Exploit mechanism: An attacker sends specially crafted commands to the router via the IGD protocol, opening ports or redirecting traffic. For example, a malicious Flash application could use UPnP to open port 80 on the firewall and forward it to an internal server.
• Scope: NAT routers running firmware that supports the Internet Gateway Device (IGD) Standardized Device Control Protocol are affected. Specific versions depend on the router manufacturer.

3. Detection and Assessment

You can confirm if a system is vulnerable by checking for UPnP service availability and listening ports. A thorough method involves analysing network traffic for IGD-related commands.

• Quick checks: Use `netstat -an | grep 49152` to check if port 49152 (the default UPnP port) is open.
• Scanning: Nmap can detect UPnP services using the script `nmap –script upnp-info `. This is an example only, results may vary.
• Logs and evidence: Router logs might show UPnP requests and responses. Look for entries related to IGD or port forwarding attempts. Specific log locations depend on the router model.

netstat -an | grep 49152

4. Solution / Remediation Steps

Fix this issue by filtering incoming traffic to the UPnP port or disabling the service entirely. These steps should be performed carefully, as disabling UPnP may affect some applications.

4.1 Preparation

• Ensure you have console or web access to the router for recovery. A roll back plan is to restore the previous configuration file.
• Changes should be made during a scheduled maintenance window, with approval from the network team lead.

4.2 Implementation

1. Step 1: Log in to your router’s web interface.
2. Step 2: Navigate to the UPnP settings (usually found under Advanced Settings or Security).
3. Step 3: Disable the UPnP service if possible.
4. Step 4: If disabling is not an option, filter incoming traffic on port 49152 using your router’s firewall rules.

4.3 Config or Code Example

Before

UPnP: Enabled

After

UPnP: Disabled

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this issue. Least privilege reduces the impact of exploitation, and input validation blocks unsafe data.

• Practice 1: Implement least privilege by restricting access to router configuration settings.
• Practice 2: Use input validation on any web interfaces that allow user-supplied data.

4.5 Automation (Optional)

No suitable automation script is available for all routers, as configurations vary widely.

5. Verification / Validation

Confirm the fix by checking if port 49152 is no longer open and re-running the earlier detection methods. A smoke test should verify basic network connectivity.

• Post-fix check: Run `netstat -an | grep 49152`. The output should be empty, indicating the port is closed.
• Re-test: Re-run the Nmap scan (`nmap –script upnp-info `). It should no longer detect UPnP services.
• Smoke test: Verify you can still access internet websites and external resources.
• Monitoring: Monitor router logs for any unexpected UPnP activity or port forwarding attempts.

netstat -an | grep 49152

6. Preventive Measures and Monitoring

Update security baselines to include disabling UPnP by default, if possible. Add checks in CI/CD pipelines to prevent the same fault.

• Baselines: Update your router security baseline or policy to recommend disabling UPnP unless absolutely necessary.
• Pipelines: Implement static analysis tools (SAST) to check for insecure configurations during deployment.
• Asset and patch process: Review router firmware updates regularly and apply patches promptly.

7. Risks, Side Effects, and Roll Back

Disabling UPnP may break some applications that rely on it. If this happens, you can re-enable the service and configure specific port forwarding rules instead.

• Risk or side effect 1: Disabling UPnP might prevent certain online games or media streaming services from working correctly.
• Risk or side effect 2: Some applications may require automatic port forwarding, which will no longer function if UPnP is disabled.
• Roll back: Step 1: Log in to your router’s web interface. Step 2: Navigate to the UPnP settings. Step 3: Re-enable the UPnP service.

8. References and Resources

• Vendor advisory or bulletin: Check your router manufacturer’s website for specific UPnP security advisories.
• NVD or CVE entry: https://nvd.nist.gov/vuln/detail/361684
• Product or platform documentation relevant to the fix: Refer to your router’s user manual for instructions on disabling UPnP and configuring firewall rules.