Cisco Unified IP Phone 7900 Series

Cisco Security Notice: Response to BugTraq - The Trivial Cisco IP Phones Compromise

Document ID: 27150

Revision 1.0

For Public Release 2002 September 20


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The original report can be found at: Cisco responded with the following which is also archived at

To:  BugTraq 
Subject:  Re: The Trivial Cisco IP Phones Compromise 
Date:  Sep 19 2002 8:32PM 
Author:  Jim Duncan <jnduncan cisco com> 
Message-ID:  <> 
In-Reply-To:  <001d01c25fce$db323e80$0a01a8c0@joshua> 

Ofir Arkin writes:
> The referred paper lists several severe vulnerabilities with Cisco
> systems' SIP-based IP Phone 7960 and its supporting environment. These
> vulnerabilities lead to: complete control of a user's credentials; total
> subversion of a user's settings for the IP Telephony network, and the
> ability to subvert the entire IP Telephony environment. Malicious access
> to a user's credentials could enable "Call Hijacking", "Registration
> Hijacking", "Call Tracking", and other voice related attacks. The
> vulnerabilities exist with any deployment scenario, but this paper deals
> specifically with large scale deployments as recommended by Cisco.
> A PDF version of the paper is available from:

This message contains Cisco responses to the issues described in the
white paper referenced above.

1.  Access to the Cisco 7960 IP phone:

    A Cisco model 7960 IP phone running a SIP-compatible image has a
    password that can be set by the IP phone administrator.  The default
    password is "cisco" if the password has not been set to some other
    value.  Cisco strongly recommends setting the password to something
    other than the default.

    The key sequence of "**#" is not intended as a password.  It is
    clearly and publicly documented in many places within Cisco's
    product literature.  The key sequence is solely intended to protect
    against casual or accidental changes to the phone's configuration.

2.  Abuse of the TFTP service:

    Although the author is correct that various attacks against the TFTP
    service can be mounted, there are several measures that can be
    employed by the IP phone administrator and the organization to
    mitigate the risk. 

    If the network is firewalled properly so that the different network
    segments are compartmentalized as the Cisco SAFE white papers
    recommend, then the TFTP server will only respond to legitimate
    requests.  The TFTP server does not need to reside on the same
    network segment as the IP phone.  If RFC 1918 addressing is employed
    for the IP phones and proper ingress/egress filtering is in place as
    recommended, then any such attack is highly unlikely to succeed from
    outside the enterprise VoIP network, even with the use of UDP.
    Access to the physical networks from within the enterprise may make
    it easier to succeed with the attack, but if the VLANs are properly
    protected and MAC addresses monitored per the SAFE documents -- for
    example, by using arpwatch or arpsnmp -- then an attack may be
    detected by the IP phone administrators. 

3.  Manual modification of the IP phone configuration:

    At some level, successful attacks would require such physical access
    to the local network segment or the IP phone that the attacker could
    simply use the IP phone itself to commit toll fraud and some of the
    other improper acts listed in the paper.  Physical access to network
    hardware is a long-standing, well-known problem in the industry.
    This is an especially important consideration for IP phones located
    in public or semi-public areas such as building lobbies.  The IP
    phone admistrator should use all available mechanisms to secure any
    IP phones that are exposed to unauthorized manipulation.

As always, Cisco is interested in protecting our customers' networks and
is continually striving to improve the security of our products.  We
appreciate the seventeen days of advance notice we received from the
author and his willingness to discuss the issue with us.  We are unaware
of any confirmed incidents of malicious exploitation of the issues in
the author's paper and ask that any such exploitation be reported to the
Cisco PSIRT, psirt cisco com,  as soon as possible.

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Updated: Sep 20, 2002 Document ID: 27150