Netgear SSL312 Router Denial Of Service

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Helith - 0815  
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Author : Rembrandt  
Date : 2008-02-27  
Affected Software: propietary CGI  
Affected OS : Netgear embedded Linux for the SSL312 router  
Propably other devices are affected as well  
Type : Denial of Service  
  
OSVDB :   
Milw0rm :   
CVE :   
ISS X-Force: :   
  
  
Trying to fix it responsible and get in contact with the vendor:  
  
-- ZDI --  
Case Opened 2008-12-28 07:57 GMT-6  
Case Closed 2009-01-15 17:01 GMT-6  
  
"After some deliberation we have unfortunately decided that we won't be  
accepting bugs affecting NetGear products."  
-- END --  
  
Contacting Netgear and mitre.org: 2009-02-01 12:25 GTM+1  
No reaction, release : 2009-02-06 23:59 GTM+1  
  
Netgear VPN router SSL312 is proune to a remote DoS condition which can get  
triggered if somebody has access to the webinterface of the VPN router.  
The problem is related to a propietary CGI binary and makes is impossible  
for users to patch the router. Further in detail analyses will show several  
other issues like outdated third party software (e.g. the webserver) and further  
problems in the cgi-binary itself which won't get disclosed here.  
  
If you download the source code the affected binary can be found at:  
./NG_SSL312-GPL/uClinux/uC-src/real/EasyAccess/EasyAccess/www/cgi-bin/single_cgi  
  
  
Steps to reproduce:  
  
Visit the Netgear SSL312 VPN router webinterface.  
You will see a login field and a password field.  
Just enter any random data and proceed.  
  
The URL will include a path like:  
https://xxx.xxx.xxx.xxx/cgi-bin/welcome/VPN_only?err=VXNlciBMb2dpbiBGYWlsZWQ=  
  
If you modify the URL as below and resend your http request the device will  
crash and needs a hard reboot.  
  
https://xxx.xxx.xxx.xxx/cgi-bin/welcome/VPN_only?../../../../../  
  
Example network affected by this: StudiVZ  
  
Simple google dork:  
intitle:SSL-VPN intext:password inurl:/cgi-bin/welcome  
  
Workaround:  
Preventing others to gain access to the webinterface of the router prevents  
the attack.  
  
Kind regards,  
Rembrandt  
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