While the research team estimated that the number of vulnerable devices is around 200 million across Europe, they believe the total number of exploitable devices to be impossible to quantify.
"The reason for this, is that the vulnerability originated in reference software, which have seemingly been copied by different cable modems manufacturers, when creating their cable modem firmware," researchers said. "This means that we have not been able to track the exact spread of the vulnerability, and that it might present itself in slightly different ways for different manufacturers."
PROOF-OF-CONCEPT CODE AVAILABLE
The four-man research team published a white paper and a dedicated website this week with information about Cable Haunt.
"The purpose of this website, is to inform as many affected users and providers as possible, in order to improve their ability to protect themselves," they said.
The idea is to have ISPs test their devices and then release a firmware updates to patch the CAble Haunt attack vector. At the time of writing, four ISPs across Scandinavia have released patches (Telia, TDC, Get AS, and Stofa), but many others across Europe have not, or aren't even aware of this security flaw.
Furthermore, due to the reasons explained above, the research team wasn't able to test all Broadcom-based cable modem models in use today. Although they confirmed that some cable modems are vulnerable (see table below), many cable modem models remain untested.
The researchers have published proof-of-concept code that ISPs and tech-savvy users can use and test their cable modem and see if it's vulnerable to a Cable Haunt attack.