NETGEAR Wireless Cable Modem Gateway Auth Bypass and CSRF

Release Date. 20-Sep-2011
Last Update. -
Vendor Notification Date. 22-Mar-2011
Product. NETGEAR Wireless Cable Modem Gateway
CG814WG
Affected versions. Hardware 1.03,
Software V3.9.26 R14 verified,
possibly others
Severity Rating. High
Impact. Authentication bypass,
Cross Site Request Forgery
Attack Vector. Remote without authentication
Solution Status. Upgrade to R15 (by contacting NETGEAR)
CVE reference. Not yet assigned

Details.
The NETGEAR Wireless Cable Modem Gateway CG814WG is supplied by ISP's
as customer premises equipment within Australia and abroad. It is a
centrally managed ISP solution whereby each ISP's devices run a
customised firmware and configuration changes and updates can be pushed
out as required.

Basic authentication is used as the primary and only authentication
mechanism for the administrator interface on the device. The basic
authentication can be bypassed by sending a valid POST request to the
device without sending any authentication header. The response from the
device sends the user to another page that requests basic
authentication, however at this point the request has already been
processed.

An example of attacks using the basic authentication bypass may include
changing the admin password or enabling the remote admin interface
(Internet facing).

Additionally, due to the lack of CSRF protection in the web application,
the bypass attack can be coupled with CSRF to have a victim enable the
remote admin interface to the Internet, where an attacker can then use
the bypass attack again across the remote admin interface to reset the
admin password and access the device. This attack is possible when
targeting a victim that is behind the NETGEAR device on the same segment
as the web administrator interface whom has browsed to a malicious site
containing the CSRF attack.

NETGEAR was notified of this vulnerability on 22 March 2011, but we
never received a response or acknowledgement of the issue or fix. Sense
of Security notified local ISP's and it was escalated by a local ISP
who worked with NETGEAR to develop and test an update. Sense of Security
was never provided an opportunity to validate the fixes in the latest
firmware version. Given the severity of the issue it would be prudent
for NETGEAR to notify and supply an update to all of its customers.

Proof of Concept.
By embedding the below HTML in a website and having a
victim browse to the website the remote management interface to the
Internet would be enabled. An attacker could then use one of the
hardcoded passwords for the device to access it, or use a basic
authentication bypass to change the admin password. Alternatively, the
attacker could conduct a CSRF attack that implements two POST requests
to have the remote admin interface enabled, and the admin password
changed.

The example here is a basic proof of concept, more complex examples
which include JavaScript redirects to mask the basic authentication
pop-up would be more stealthy.

Solution.
Ask your ISP to obtain the latest firmware from NETGEAR and deploy it
to your device.

Discovered by.
Sense of Security Labs.

About us.
Sense of Security is a leading provider of information
security and risk management solutions. Our team has expert
skills in assessment and assurance, strategy and architecture,
and deployment through to ongoing management. We are
Australia's premier application penetration testing firm and
trusted IT security advisor to many of the country's largest
organisations.

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Sydney NSW 2000
AUSTRALIA

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The latest version of this advisory can be found at:

Click to access SOS-11-011.pdf