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AA-2007.0021                  AUSCERT Advisory

                             [Win][UNIX/Linux]
    Multiple browsers handling of PASV FTP responses may port scanning
                               28 March 2007
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        AusCERT Advisory Summary
        ------------------------

Product:              KDE Konqueror 3.5.6 and prior versions
                      Mozilla Firefox versions prior to 2.0.0.3
                      Mozilla Firefox versions prior to 1.5.0.11
                      Opera 9.10
Operating System:     UNIX variants (UNIX, Linux, OSX)
                      Windows
Impact:               Reduced Security
Access:               Remote/Unauthenticated
CVE Names:            CVE-2007-1562 CVE-2007-1563 CVE-2007-1564
Member content until: Wednesday, April 25 2007


OVERVIEW:
        
        A paper [1] has been released discussing the potential for abuse of 
        web browsers due to their FTP protocol implementation. This 
        vulnerability results in the web browser being used as a port 
        scanner. When the handling of the PASV FTP response by Mozilla 
        Firefox, Opera and KDE Konqueror the browser can be instructed to 
        connect to an arbitrary host and port.


IMPACT: 

        When this functionality is combined with Javascript it can allow a 
        malicious FTP server to initiate a port scan of an organisation's 
        internal network, via web browsers. A proof of concept 
        demonistrating many elements of this attack has been included with 
        the paper.

        Internet Explorer is reported as not vulnerable to this issue.


MITIGATION:

        Mozilla has acknowledged this vulnerability [2] and released Firefox 
        versions 2.0.0.3 and 1.5.0.11 correcting it. KDE have also 
        acknowledged this vulnerability [3] and made patches are available.
        As yet, this issue has not been acknowledged by Opera.

        A partial mitigation strategy may be the filtering of PASV responses 
        which direct clients away from an originating FTP server.


REFERENCES:

        [1] Manipulating FTP Clients Using The PASV Command
            http://bindshell.net/papers/ftppasv/ftp-client-pasv-manipulation.pdf

        [2] Mozilla Foundation Security Advisory 2007-11
            http://www.mozilla.org/security/announce/2007/mfsa2007-11.html

        [3] KDE Security Advisory: KDE ioslave PASV port scanning vulnerability
            http://www.kde.org/info/security/advisory-20070326-1.txt


AusCERT has made every effort to ensure that the information contained
in this document is accurate.  However, the decision to use the information
described is the responsibility of each user or organisation. The decision to
follow or act on information or advice contained in this security bulletin is
the responsibility of each user or organisation, and should be considered in
accordance with your organisation's site policies and procedures. AusCERT
takes no responsibility for consequences which may arise from following or
acting on information or advice contained in this security bulletin.

If you believe that your computer system has been compromised or attacked in 
any way, we encourage you to let us know by completing the secure National IT 
Incident Reporting Form at:

        http://www.auscert.org.au/render.html?it=3192

===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
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