Cisco already developed a fix for the vulnerability reported in the WRT54GL model and is working with DefenseCode to validate it, a Cisco representative said Friday via email. "The fix will be released for customers as soon as possible, but in the meantime those using the WRT54GL can stay safe by ensuring their wireless network is securely configured, and the only people using an Ethernet cable for connecting to the router are friends," according to the Cisco official.
The Cisco Product Security Incident Response Team (PSIRT) is investigating DefenseCode's claim that additional Cisco products, including WRT54G3G and WRT310N, might be vulnerable, but nothing can be confirmed at this time, the Cisco representative said.
However, customers who wish to disable the UPnP functionality in Linksys routers can follow the instructions in a technical support document published earlier this week in response to the UPnP vulnerabilities reported by Rapid7.
DefenseCode focused its investigation of this vulnerability on routers, but if the Broadcom UPnP stack is also used in other network-enabled devices like printers, media servers, IP cameras and smart TVs, then those devices are probably vulnerable as well, Juranic said. "But we didn't research other devices, so we can't be sure," he said.
Rapid7 researchers said Monday in their UPnP research paper that more than 15 million devices that responded to UPnP requests from the Internet were using "a commercial stack that is likely developed by Broadcom." They referred to this implementation as "Unknown SDK 1" and said that it was the third most commonly used UPnP stack after Intel/Portable UPnP SDK and MiniUPnP SDK.
Juranic is confident that "Unknown SDK 1" from Rapid7's paper is the vulnerable Broadcom UPnP SDK identified by DefenseCode.
Rapid7 did not immediately respond to a request to confirm this on Friday, but a Thursday Twitter message from HD Moore, Rapid7's chief security officer, suggests that Juranic is correct. "DefenseCode identified a format string in the Broadcom UPnP SOAP service (around ~15m hosts as identified by Rapid7)," he wrote.
However, though having the UPnP service exposed to the Internet increases the chances of a device being attacked, it is not a prerequisite for exploiting the vulnerability found by DefenseCode or the ones found by Rapid7 in UPnP implementations. An attacker who gains access to a local network can also exploit these vulnerabilities to hack into UPnP-enabled networked devices.