Easy-to-exploit authentication bypass flaw puts Netgear routers at risk

February 1, 2017 – 4:02 PM

For the past half year Netgear has been working on fixing a serious and easy-to-exploit vulnerability in many of its routers. And it’s still not done.

While Netgear has worked to fix the issue, the list of affected router models increased to 30, of which only 20 have firmware fixes available to date. A manual workaround is available for the rest.

The vulnerability was discovered by Simon Kenin, a security researcher at Trustwave, and stems from a faulty password recovery implementation in the firmware of many Netgear routers. It is a variation of an older vulnerability that has been publicly known since 2014, but this new version is actually easier to exploit.

In January 2014, a researcher found that he could trick the web-based management interface of Netgear WNR1000v3 routers to disclose the admin’s password. The exploit involved passing a numerical token obtained from one script called unauth.cgi to another called passwordrecovered.cgi. Neither of them required authentication to access.

Last year, Kenin came across this old exploit when he wanted to break into his own router — a different Netgear model — and realized that it worked. The researcher decided to write a script to automate the exploit so that other people could test their own router models, but due to a programming error the script didn’t pass the correct token to passwordrecovered.cgi. Yet the exploit still worked.


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