What is the Open Portmapper Vulnerability?

You may have recently received a letter and/or email from Virgin Media explaining that we have been notified that a device on your network has a vulnerability known as an Open Portmapper vulnerability. If you have received such a communication from us, please follow the advice given on this page to help resolve the issue.

Overview

There is a design flaw that exists in the Portmapper service currently in use on a device on your home network. Portmapper, also known as RPC Bind or RPC Portmap, is a service used by computer systems to assist with networking tasks.

This flaw can allow remote 3rd party attackers to gain unauthorised access and perform Distributed Denial of Service (DDoS) attacks against target machines. A remote attacker can leverage this flaw by sending a specially crafted request to an affected Portmapper server.

What has happened?

We work with a number of not-for-profit organisations across the banking industry and security sectors that collate information on devices across the Internet that appear to be compromised or misconfigured. This means that your compromised or misconfigured device is publicly accessible on the Internet, and therefore the scanning that is performed by these organisations is not within your private network.

We suspect a device connected to your home network may have an open Portmapper vulnerability.

For more information on these reports please visit portmapperscan.shadowserver.org*

If the settings are left open they can be exploited to unwittingly participate in malicious activities, for example a Distributed Denial of Service (DDoS) attack.

It is therefore important that you follow the advice in this article. **
 

How can the issue be fixed?
 

The easiest way to deal with an open Portmapper vulnerability is to configure your firewall to block UDP port 111.

It is worth noting that blocking this port will only stop traffic over this port leaving or entering your home network. Services within your home that use this port should continue to work as normal.

Hub 3.0

To close the vulnerable port on the Hub 3.0:

  • Access your Hub's configuration page - default web address: 192.168.0.1
  • Login with your username and password, default will be shown on the Hub itself
  • Select Security on the left side of the page
  • Select the Port Forwarding option
  • Remove any rules that will keep port 111 open
  • Select the Port Triggering option
  • Remove any rules that will keep port 111 open

Virgin Media Super Hub

To close the vulnerable port on the Super Hub 1 or 2’s firewall:

  • Access your Hub's configuration page - default web address: 192.168.0.1
  • Login with your username and password, default will be shown on the Hub itself
  • Select Advanced Settings and accept the prompt
  • Scroll down to the Security section
  • Select the Port Forwarding option
  • Tick the Delete box next to any rules that will keep port 111 open
  • Click the Apply option
  • Select the Port Triggering option
  • Tick the Delete box next to any rules that will keep port 111 open
  • Click the Apply option

3rd party routers

If you use a 3rd party router in conjunction with the Virgin Media Super Hub or Hub 3.0, your router's firewall will need to be configured to ensure port 111 is not accessible outside of your local network - this can be performed by blocking the port or removing any Port Forwarding rules for that port. In order to identify how to do this with your particular router, refer to the documentation for your device or refer to the manufacturer's website.

It is important to check all your devices sit behind a firewall. In most cases your firewall is configured as a part of your router, this is the case with the Hub 3.0 and Virgin Media Super Hub. If you have specifically disabled the Firewall in your router, it is crucial that you configure your devices to sit behind a firewall that is blocking port 111. If this does not apply to you, please proceed to the next step.

Modem Mode - If you are using your Virgin Media Super Hub or Hub 3.0 in Modem Only mode, it is essential that you are using a firewall on any device or router that is plugged directly into the Hub. When in Modem Only mode, your Hub does not operate with a firewall. If this does not apply to you, please proceed to the next step.

DMZ - Most firewalls, including the one provided with the Virgin Media Super Hub and Hub 3.0 include a DMZ option. This feature allows for a device using a specific local IP address on your home network (e.g. 192.168.0.2) to bypass your Firewall settings. This is occasionally necessary if you are using a device that has its own firewall configured. If you have a device configured in your firewall's DMZ that does not use its own firewall, it is crucial that you disable this option immediately. Computers operating without a firewall are extremely vulnerable to attack as all ports are essentially exposed to the wider Internet.

To check if a device is configured in the DMZ on your Hub 3.0:

  • Access your Hub's configuration page - default web address: 192.168.0.1
  • Login with your username and password, default will be shown on the Hub itself
  • Select Security on the left side of the page
  • Select the DMZ option
  • To remove a device from the DMZ, tick the Disable box

To check if a device is configured in the DMZ on your Virgin Media Super Hub 1 or 2:

  • Access your Hub's configuration page - default web address: 192.168.0.1
  • Login with your username and password, default will be shown on the Hub itself
  • Select Advanced Settings
  • Select DMZ
  • To remove a device from the DMZ, uncheck the tick box at the top of the page
     

Where can I find further information and advice?

If you’d like further advice then our forum community will be happy to help. Just visit virginmedia.com/community and join the conversation on our Security Matters board.

You can find general security advice and articles on other vulnerabilities by checking Security Hub at virginmedia.com/securityhub

Note: This article is intended to provide advice. Virgin Media is not responsible for any issues encountered in the course of resolving the issue and is not able to provide any technical support for such problems.
 

*Links to external sites are provided as a courtesy and virgin media is not responsible for the content of these sites or any issues encountered as a result of  applying information from these sites. Virgin media are not able to provide any technical support for such problems.

**These fixes are provided as a courtesy and we are not responsible for any problems encountered whilst applying these steps and we are not able to provide any technical support for such problems.


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