Enterprises with a lot of remote offices and shadow IT running small office-home office (SOHO) networking equipment have got to worry about yet another risk this week. A new piece of research from Rapid7 shows that a protocol found in SOHO routers, firewalls, and gateways is wide open to some pretty nasty attacks. And according to early reports, as many as 1.2 million devices could be vulnerable.

According to Jon Hart, senior security researcher at Rapid7, the problems present themselves in NAT-PMP, a protocol that is intended to be used by internal, assumed trusted users to manipulate firewall and routing rules in order to let external users access internal TCP and UDP services such as file and media sharing services. The problem is that the bulk of the security mechanisms for the service "rely on proper implementation of the protocol and a keen eye on the configuration of the service(s) implementing NAT-PMP," Hart writes, reporting that as a part of Rapid7's Project Sonar, widespread scanning online found more than a million NAT-PMP devices vulnerable to five big classes of exploitation.

These include interception of internal NAT traffic, interception of external traffic, unauthorized access to internal NAT client services, denial-of-service against host services and information disclosure about the NAT-PMP device. Of particular concern is the potential for interception of external traffic, which was found on 86 percent of devices that responded to Hart's scan.

"This attack can also be used to cause the NAT-PMP device to respond to and forward traffic for services it isn't even listening on. For example, if the NAT-PMP device does not have a listening HTTP service on the external interface, this same flaw could be used to redirect inbound HTTP requests to another external host, making it appear that HTTP content hosted on the external host is hosted by the NAT-PMP device."

Also troubling is the fact that interception of internal NAT traffic can make it possible to create mapping of other services listening on the device, which could be leveraged for a denial-of-service attack against the device.

According to Hart, the issues are widespread across many different vendors, though his team was unable to pinpoint the specific types of devices found during scans.

"While things did seem promising at first when our correlation started hinting that the problem was widespread across dozens of products from a variety of vendors, upon acquiring a representative subset of these products and performing the testing in our lab we were unable to identify situations in which these products could be vulnerable to the NAT-PMP vulnerabilities discussed in this advisory," he wrote, explaining that they were unable to pinpoint products due to legal and technical complexities but that, "it is entirely possible, perhaps even likely, that these vulnerabilities are present in popular products in default or supported configurations."

Hart says the vulnerabilities found in his research are "not theoretical," but that it's unknown how many devices on the public Internet are actually vulnerable to the more severe interception issues he's laid out.

"For consumers with NAT-PMP capable devices on your network, you should ensure that all NAT-PMP traffic is prohibited on un-trusted network interfaces," he warns.