Advisory ID: cisco-sa-20020522-ip-phone-vulnerability
For Public Release 2002 May 22 16:00 UTC (GMT)
Several vulnerabilities have been identified and repaired in Cisco IP
Phones. One vulnerability allows unauthorized modification of the phone's
configuration, while the remainders cause the phone to restart when certain
types of network traffic are received.
Workarounds are available for some of the vulnerabilities. Cisco is
offering free fixed software to address these vulnerabilities. Full details are
available below and in the on-line copy of this document at
This section provides details on affected products.
Cisco IP Phone models 7910, 7940, and 7960 are the only Cisco products
affected by these vulnerabilities.
No other Cisco products are currently known to be affected by these
The Cisco IP Phones are vulnerable to several network based Denial of
Service (DoS) attacks including the well-known attacks for "jolt", "jolt2",
"raped", "hping2", "bloop", "bubonic", "mutant", "trash", and "trash2". All of
these defects were resolved by improving the ability of the IP Phone to resist
high rates of traffic directed at the IP Phone.
The Cisco IP phones include a built-in web server on port 80. The
server provides several pages of debug and status information about the phone.
It is possible to modify an HTTP request to exploit an input validation
vulnerability which results in the reinitialization of the IP phone.
The Cisco IP Phones store their configuration information locally and
most of it is accessible through the "Settings" button on the phone. By
default, these settings are locked (as indicated by a padlock icon in the mode
title bar when viewing them) to prevent them from being changed accidentally.
These settings may be modified via a trusted path key combination: '**#'. This
is documented in the product manual and is not admin-configurable. Once
unlocked, several fields can be reconfigured. Modification of the phone's
configuration is very likely to go unnoticed, since a user never has to
interact with the configuration menu where these changes were made. This will
be resolved at a later date likely by a configuration option to control the
ability to make local configuration changes at the keypad of the phone.
Cisco has provided scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this Security Advisory is done in accordance with CVSS version 2.0.
CVSS is a standards-based scoring method that conveys vulnerability severity and helps determine urgency and priority of response.
Cisco has provided a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.
Cisco has provided an FAQ to answer additional questions regarding CVSS at
Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at
Cisco IP Phones can be forced to restart by an attacker using any of a
variety of widely available, well-known DOS programs if the attacker can
successfully transmit packets to the IP Telephone. The phone may also restart
in the event it receives a crafted HTTP request with invalid arguments directed
at the phone. Any call in progress on the affected IP Phone will be
disconnected, and the IP Phone will not be useable until it has finished
restarting and resumed normal operation. This attack can be repeated
Cisco IP phones running a SIP or MGCP image are subject to the same
widely available denial-of-service programs but are not susceptible to a
web-based attack as those images do not include a web interface.
Normal operation of Cisco IP Phones can be subverted if an attacker
obtains local physical access to the IP Phone and reconfigures it, possibly
forcing it to download software or configuration information of his or her own
choosing. A successful attacker could gain full control over the operation of
the IP Phone and any call setup requests and responses made between the IP
Phone and Cisco CallManagers or other VoIP gateways.
When considering software upgrades, also consult
and any subsequent advisories to determine exposure and a complete upgrade
In all cases, customers should exercise caution to be certain the
devices to be upgraded contain sufficient memory and that current hardware and
software configurations will continue to be supported properly by the new
release. If the information is not clear, contact the Cisco Technical
Assistance Center ("TAC") or your contracted maintenance provider for
Cisco IP Phone Firmware (fixes carry forward into all later
CallManager Version Affected
First Fixed Firmware Release.
First Fixed CallManager Release.
P00303020203 (available 2002-05-29)
Cisco IP Phone SIP or MGCP Firmware (fixes carry forward into all
First Fixed Firmware Release.
POS3-03-1-00 and earlier
POM3-03-1-00 and earlier
Denial-of-service attacks on the Cisco IP Phone can be mitigated by
limiting or blocking IP traffic from untrusted sources. Exploitation of the web
interface vulnerability can be provided by blocking access to port 80 via other
devices on the network. The basic configuration of the Cisco IP Telephone can
be protected by permitting physical access only by authorized users and network
Cisco has made free software available to address this vulnerability
for affected customers. Prior to deploying software, customers should consult
their maintenance provider or check the software for feature set compatibility
and known issues specific to their environment.
Customers may only install and expect support for the feature sets they
have purchased. By installing, downloading, accessing or otherwise using such
software upgrades, customers agree to be bound by the terms of Cisco's software
license terms found at
or as otherwise set forth at Cisco.com Downloads at
Do not contact either "firstname.lastname@example.org" or "email@example.com"
for software upgrades.
Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades should be
obtained through the Software Center on Cisco's worldwide website at
Customers whose Cisco products are provided or maintained through prior
or existing agreement with third-party support organizations such as Cisco
Partners, authorized resellers, or service providers should contact that
support organization for guidance and assistance with the appropriate course of
action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific
customer situations such as product mix, network topology, traffic behavior,
and organizational mission. Due to the variety of affected products and
releases, customers should consult with their service provider or support
organization to ensure any applied workaround or fix is the most appropriate
for use in the intended network before it is deployed.
Customers who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain software patches and bug fixes by contacting the Cisco Technical Assistance Center (TAC). TAC
contacts are as follows.
+1 800 553 2447 (toll free from within North America)
+1 408 526 7209 (toll call from anywhere in the world)
Have your product serial number available and provide the URL of this notice as evidence of entitlement to a software patch or bug fix. Customers without service contracts should request a software patch or bug fix through the TAC.
for additional TAC contact information, including special localized telephone
numbers and instructions and e-mail addresses for use in various
The vulnerabilities described by CSCdx21102 and CSCdx21108 were
originally reported to Cisco by Johnathan Nightingale. The Cisco PSIRT is not
aware of any public announcements or malicious use of the vulnerabilities
described in this advisory.
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.
This notice will be posted on Cisco's Worldwide Web site at
In addition to Worldwide Web posting, a text version of this notice is
clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail
and Usenet news recipients:
firstname.lastname@example.org (includes CERT/CC)
Various internal Cisco mailing lists
Future updates of this notice, if any, will be placed on Cisco's
Worldwide Web server, but may or may not be actively announced on mailing lists
or newsgroups. Users concerned about this problem are encouraged to check the
URL given above for any updates.
Change status from Interim to Final
Initial public release