Netgear DGN Authentication Bypass / Command Execution

`Unauthenticated command execution on Netgear DGN devices  
========================================================  
  
[ADVISORY INFORMATION]  
Title: Unauthenticated command execution on Netgear DGN devices  
Discovery date: 01/05/2013  
Release date: 31/05/2013  
Credits: Roberto Paleari ([email protected], twitter: @rpaleari)  
  
[VULNERABILITY INFORMATION]  
Class: Authentication bypass, command execution  
  
[AFFECTED PRODUCTS]  
This security vulnerability affects the following products and firmware  
versions:  
* Netgear DGN1000, firmware version < 1.1.00.48  
* Netgear DGN2200 v1  
Other products and firmware versions are probably also vulnerable, but they  
were not checked.  
  
[VULNERABILITY DETAILS]  
Attackers can leverage this vulnerability to bypass existing authentication  
mechanisms and execute arbitrary commands on the affected devices, with root  
privileges.  
  
Briefly, the embedded web server skips authentication checks for some URLs  
containing the "currentsetting.htm" substring. As an example, the following URL  
can be accessed even by unauthenticated attackers:  
  
http://<target-ip-address>/setup.cgi?currentsetting.htm=1  
  
Then, the "setup.cgi" page can be abused to execute arbitrary commands. As an  
example, to read the /www/.htpasswd local file (containing the clear-text  
password for the "admin" user), an attacker can access the following URL:  
  
http://<target-ip-address>/setup.cgi?next_file=netgear.cfg&todo=syscmd&cmd=cat+/www/.htpasswd&curpath=/&currentsetting.htm=1  
  
Basically this URL leverages the "syscmd" function of the "setup.cgi" script to  
execute arbitrary commands. In the example above the command being executed is  
"cat /www/.htpasswd", and the output is displayed in the resulting web  
page. Slightly variations of this URL can be used to execute arbitrary  
commands.  
  
[REMEDIATION]  
For DGN1000, Netgear included a fix for this issue inside firmware version  
1.1.00.48. According to Netgear, DGN2200 v1 is not supported anymore, while v3  
and v4 should not be affected by this issue; these versions were not tested by  
the author.  
  
[DISCLAIMER]  
The author is not responsible for the misuse of the information provided in  
this security advisory. The advisory is a service to the professional security  
community. There are NO WARRANTIES with regard to this information. Any  
application or distribution of this information constitutes acceptance AS IS,  
at the user's own risk. This information is subject to change without notice.  
`