The VoIP phones of snom technology AG can be configured, monitored or controlled with a browser connecting to the built in web interface. It is strongly recommended to enable authentication on the web interface and to set a strong password. By constructing a specially crafted HTTP request the authentication of the web interface can be completely bypassed.
Access to the web interface without authentication enables a malicious user to 2: - call expensive numbers - listen to the phone conversation by capturing the network traffic - read SIP username and password - read and modify all configuration parameters of the phone - redirect phone calls to another VoIP server - activate the microphone and listen to the conversation in the room
The web interface of the Snom VoIP/SIP phones is protected by Basic Authentication or Digest Authentication. The authentication can be completely bypassed by modifying the HTTP request. A normal browser sets the request header "Host:" to the IP address or the host name that is entered in the URL field of the browser. If the request header is modified to contain the value "Host: 127.0.0.1", all pages and functions of the web interface can be reached without prompting the user to authenticate.
curl -H "Host: 127.0.0.1" http://<IP address of phone>/ curl -k -H "Host: 127.0.0.1" https://<IP address of phone>/
-> if the phone is vulnerable, the index page of the web interface is returned -> if the phone is not vulnerable, an "HTTP/1.1 401 Unauthorized" response is returned
Vendor Notified: March 19, 2009
Vendor Status: Replied on March 19 and March 30, vulnerability
Vendor Response: Problem fixed in firmware version 7.1.39/7.3.14. Problem will be fixed in version 6. Patch available: Firmware upgrade to versions 6.5.20, 7.1.39, 7.3.14 and above