How to remediate – UPnP Internet Gateway Device (IGD) Port Mapping Manipulation

1. Introduction

The UPnP Internet Gateway Device (IGD) Port Mapping Manipulation vulnerability allows unauthorised addition of port redirections to a router. This can create openings in a firewall, potentially exposing internal services directly to the internet. Routers supporting the IGD standard are usually affected. A successful exploit could compromise confidentiality, integrity and availability of systems behind the router.

2. Technical Explanation

The vulnerability occurs because routers incorrectly handle Universal Plug and Play (UPnP) requests. Specifically, they allow adding port mappings without authentication. An attacker can send specially crafted UPnP commands to redirect external ports on the router to an internal IP address controlled by them. This allows bypassing firewall rules. The remote device is a NAT router that supports the Internet Gateway Device (IGD) Standardized Device Control Protocol.

• Root cause: Lack of authentication for adding port mappings via UPnP IGD.
• Exploit mechanism: An attacker sends SOAP requests to the router’s UPnP interface, creating port forwarding rules. For example, a JavaScript script embedded in a malicious webpage could trigger these requests.
• Scope: Routers supporting the Internet Gateway Device (IGD) standard are affected. Specific models and firmware versions were not specified in the provided context.

3. Detection and Assessment

Confirming vulnerability involves checking for UPnP IGD support and whether port mappings can be added without authentication. Nessus identified this issue, but manual checks are also possible.

• Quick checks: Check your router’s web interface for UPnP settings. If enabled, investigate further.
• Scanning: Nessus vulnerability ID 361684 detects this issue. Other scanners may have similar signatures.
• Logs and evidence: Router logs might show UPnP requests attempting to add port mappings. The specific log location varies by router vendor.

nmap --script upnp-info -p 5000 

4. Solution / Remediation Steps

The primary solution is to disable the IGD service or restrict access to trusted networks.

4.1 Preparation

• Note any services that rely on UPnP functionality and may be affected by disabling it. A roll back plan involves restoring the original configuration if issues occur.
• A change window may be needed, depending on service impact. Approval from a network administrator is recommended.

4.2 Implementation

1. Step 1: Log in to your router’s web interface.
2. Step 2: Navigate to the UPnP settings (usually under Advanced or Firewall).
3. Step 3: Disable UPnP if possible.
4. Step 4: If disabling is not an option, restrict access to trusted IP addresses only.

4.3 Config or Code Example

Before

UPnP: Enabled, Allow all connections

After

UPnP: Disabled

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this issue.

• Practice 1: Least privilege – only enable necessary services and features on your router.
• Practice 2: Network segmentation – isolate sensitive internal networks from direct exposure to the internet.

4.5 Automation (Optional)

Automation is unlikely for this specific issue due to varying router interfaces, but configuration management tools can be used to enforce UPnP settings across multiple devices.

# Example Ansible task - replace with your router's API or CLI commands
- name: Disable UPnP on router
  ansible.builtin.shell: "routerctl upnp disable" #Replace with actual command
  delegate_to: "{{ inventory_hostname }}"

5. Verification / Validation

Confirm the fix by checking that port mappings can no longer be added without authentication.

• Post-fix check: Attempt to add a port mapping using a tool like `netcat` or a UPnP testing script. The request should fail.
• Re-test: Re-run the Nessus scan (ID 361684). It should no longer report the vulnerability.
• Monitoring: Check router logs for failed UPnP requests, which could indicate ongoing attempts to exploit the vulnerability.

nmap --script upnp-info -p 5000  #Should show reduced functionality or no response

6. Preventive Measures and Monitoring

Regular security assessments and updates are key to preventing this type of vulnerability.

• Baselines: Update your router’s firmware regularly with the latest security patches.
• Pipelines: Consider using a configuration management tool to enforce secure UPnP settings across all routers.
• Asset and patch process: Implement a regular patching cycle for all network devices, including routers.

7. Risks, Side Effects, and Roll Back

Disabling UPnP may break some applications or services that rely on it.

• Risk or side effect 2: Port forwarding rules configured manually will still work, but new ones cannot be added automatically.
• Roll back: Step 1: Log in to your router’s web interface. Step 2: Re-enable UPnP if necessary. Step 3: Restore the original configuration from backup if issues persist.

8. References and Resources

Links to resources related to this specific vulnerability.

• Vendor advisory or bulletin: Not provided in context.
• NVD or CVE entry: Not provided in context.
• Product or platform documentation relevant to the fix: https://github.com/filetofirewall/fof, https://www.gnucitizen.org/blog/flash-upnp-attack-faq/