A New Critical Vulnerability in SAGEMCOM routers could allow an attacker to gain access control

In the configuration backup feature, the SAGEMCOM router, model [email protected] NET, operating software version NET 4.109.0, has an Inappropriate Access Control flaw.

16:45 GMT, Friday, November 27, 2020

This router is widely sold to its customers in Brazil through ISP provider CLARO.

The flaw occurs when the router’s user interface has a legitimate session running.

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

Make a request to the /backupsettings.conf path removing any cookie data.

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Request wihtout any session data

Making the request from a different IP than the one which initialized the valid session:

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curl request without any session data

The backupsettings.conf file contains sensitive information, including the administration username and password.

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If the “Remote Configuration Management” is activated in the router, the access to the backup configuration file becomes available through the WAN to all Internet at the TCP:6080 .

In the image bellow I used a web proxy and accessed the WAN IP address of the router “189.61…” to ensure the external communication.

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Upgrade the router firm to lastest version from router-network.com/sagemcom/f-st-3486