This is the explanation regarding the CVE 2020–29138 which I’ve discovered in the routers provided by the CLARO company in Brazil.

The SAGEMCOM router, model F@ST3486 NET, running the NET_4.109.0 software version, contains an Improper Access Control vulnerability in the configuration backup functionality. This router is widely distributed by the ISP provider CLARO company, for their customers in Brazil.

The vulnerability occurs when there is a valid session running in the router web interface.

As long as there is any valid session opened, any unauthenticated request to http://<router-ip>/backupsettings.conf will allow the router configuration download.

Reproducing:

Access the router’s web interface…

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