[NT] Finjan SurfinGate Bypass (URL Encoding)

From: SecuriTeam (support_at_securiteam.com)
Date: 07/05/05

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Date: 5 Jul 2005 14:04:55 +0200

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      Finjan SurfinGate Bypass (URL Encoding)
    ------------------------------------------------------------------------

    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@gmx.de> Daniel
    Schroter.

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