Unauthenticated remote code execution on D-Link ShareCenter products
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[ADVISORY INFORMATION]
Title:    Unauthenticated remote code execution on D-Link ShareCenter products
Release date:   08/02/2012
Last update:   08/02/2012
Credits:   Roberto Paleari, Emaze Networks S.p.A (roberto.paleari@emaze.net)

[VULNERABILITY INFORMATION]
Class:           Authentication bypass, remote code execution

[AFFECTED PRODUCTS]
We confirm the presence of the security vulnerabilities on the following
products/firmware versions:

   * DNS-320, firmware version 2.00.1217.2010
   * DNS-320, firmware version 2.01.0512.2011
   * DNS-320, firmware version 2.02.0901.2011
   * DNS-320, firmware version 2.02.0923.2011
   * DNS-325, firmware version 1.01.1217.2010

Other models and firmware versions are probably also vulnerable, but they were
not checked.

[VULNERABILITY DETAILS]
D-Link ShareCenter devices suffer from a publicly-known authentication bypass
issue that, according to an existing advisory[1], can be exploited to cause a
Denial-of-Service.

In this advisory we shed some light over the impact of this issue. In
particular, the device implements almost no authentication checks on HTTP
requests for any existing CGI script (i.e., all the CGIs under the /cgi
directory). As an example, an attacker may retrieve the device model & firmware
version by accessing the following resources:

  http://<device IP address>/cgi-bin/discovery.cgi
  http://<device IP address>/cgi-bin/system_mgr.cgi?cmd=get_firm_v_xml

Besides information gathering, this vulnerability can be exploited to gain full
control of the device. In particular, an undocumented functionality permits to
execute arbitrary commands, displaying their output in the generated HTML
page. As an example, to execute the "ls" command, an attacker can access the
following URL:

  http://<device IP address>/cgi-bin/system_mgr.cgi?cmd=cgi_sms_test&command1=ls

Even in this case, no authentication checks are performed.

References:
[1] http://www.securityfocus.com/bid/50902/info

[REMEDIATION] 
We are not aware of an updated firmware that corrects the issue described in
this advisory.

[DISCLOSURE TIME-LINE]
    * 22/12/2011 - Initial vendor contact.

    * 27/12/2011 - Vendor replied.

    * 28/12/2011 - Emaze asks for a technical contact to discuss the details of
             the vulnerability. Publication date set to January 18th,
             2012.

    * 02/01/2012 - No response from the vendor. The author re-sent the last
             e-mail.

    * 17/01/2012 - Still no reply from the vendor. The author re-sent the
                   e-mail, again.

    * 31/01/2012 - Sent another e-mail to vendor, to inform about the intention
             to publicly disclose the vulnerability within February, 3rd.

    * 08/02/2012 - Still no reply. Disclosure.

[COPYRIGHT]
Copyright(c) Emaze Networks S.p.A 2012, All rights reserved worldwide.
Permission is hereby granted to redistribute this advisory, providing that no
changes are made and that the copyright notices and disclaimers remain intact.

Emaze Networks has updated ipLegion, its vulnerability assessment platform, to
check for this vulnerability. Contact info@emaze.net to have more information
about ipLegion.

[DISCLAIMER]
Emaze Networks S.p.A is not responsible for the misuse of the information
provided in our security advisories. These advisories are 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.