Hundreds of millions of Broadcom-based cable modems are at risk of remote hijacking due to the presence of a vulnerability dubbed Cable Haunt, CVE-2019-19494.
The flaw resides in the hardware and software component of Broadcom chips called a spectrum analyzer that protects the cable modem from signal surges and disturbances coming via the coax cable.
“There are an estimated 200 million cable modems in Europe alone. With almost no cable modem tested
Four Danish researchers (Alexander Dalsgaard Krog (Lyrebirds), Jens Hegner Stærmose (Lyrebirds), Kasper Terndrup (Lyrebirds), Simon Vandel Sillesen (Independent)) have demonstrated how to exploit the flaw by tricking a victim into opening a specially crafted web page containing malicious JavaScript or a malicious email. Then the code connects to the web server built into the vulnerable modem on the local network and the script alters the contents of the modem’s processor registers, by overwriting the stack and triggering a buffer overflow. With this attack, it is possible to redirect execution to malicious code provided with the request and perform a broad range of malicious activities, including:
For security reasons, on most cable modems, access to the spectrum analyzer is allowed only for connections from the internal network.
The research team discovered that the Broadcom chip spectrum analyzer lacks protection against DNS rebinding attacks, uses default credentials, and its firmware contains programming bugs.
A‘DNS Rebinding’ attack allows any website to create a DNS name that they are authorized to communicate with, and then make it resolve to
This attack could allow remote attackers to take over vulnerable Broadcom-based cable modems in a stealth way.
“Cable Haunt is exploited in two steps. First, access to the vulnerable endpoint is gained through a client on the local network, such as a browser. Secondly the vulnerable endpoint is hit with a buffer overflow attack, which gives the attacker control of the modem.” the researchers explained.
The four researchers published a white paper and the dedicated website also contains a PoC exploit for the issue working with the
The Cable Haunt vulnerability affects cable modems using
Experts pointed out that firewalls could block this attack only using very specific configuration which they suspect nearly nobody to have set up.
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(SecurityAffairs – Cable Haunt, hacking)
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