[NT] Finjan SurfinGate Bypass (URL Encoding)

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  Finjan SurfinGate Bypass (URL Encoding)
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SUMMARY

The  <http://www.finjan.com/> Finjan SurfinGate allows "preforming web 
content filtering and Internet access management". A vulnerability in 
Finjan SurfinGate product allows attackers to bypass the product's access 
management and restriction (You can download files that would be otherwise 
blocked).

DETAILS

Vulnerable Systems:
 * SurfinGate version 7.0SP2 and SP3

CVE Information:
 <http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1994> 
CAN-2005-1994

An URL ASCII decode problem exists in the Finjan SurfinGate. If an 
attacker uses ASCII encoding when trying to access files through the 
Finjan SufinGate, the attacker will bypass the security policy enforced by 
the product. Due to this flaw, it is possible to bypass EXE download 
restriction, or download files that have two or more extensions, for 
example file.jpg.exe.

If the product is configured to block specific Content-Type, SurfinGate 
will block the download, but an attacker can configure a malicious web 
server to return non-blocked Content-Types.

Proof of concept:
Of course we don't take a normal exe-file. Let us use a screensaver. If 
you block SCR-files the following will be blocked:  
<http://www.mustangworld.com/ourpics/sware/Mustangworld.scr> 
http://www.mustangworld.com/ourpics/sware/Mustangworld.scr

If you just block the SCR-extension (and not the content type in your 
infrastructure) you can bypass the Finjan SurfinGate by using the 
following link:  
<http://www.mustangworld.com/ourpics/sware/Mustangworld%2escr> 
http://www.mustangworld.com/ourpics/sware/Mustangworld%2escr

Vendor Status:
Finjan Software Ltd. has been notified for a year ago, no response was 
received.


ADDITIONAL INFORMATION

The information has been provided by  <mailto:d.schroeter@xxxxxx> Daniel 
Schroter.



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