[Full-disclosure] Cisco Security Advisory: Cisco Unified IP Phone Overflow and Denial of Service Vulnerabilities



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Cisco Security Advisory: Cisco Unified IP Phone Overflow and Denial
of Service Vulnerabilities

Revision 1.0

For Public Release 2008 February 13 1600 UTC (GMT)

+--------------------------------------------------------------------

Summary
=======

Cisco Unified IP Phone models contain multiple overflow and denial of
service (DoS) vulnerabilities. There are workarounds for several of
these vulnerabilities. Cisco has made free software available to
address this issue for affected customers.

This advisory is posted at:

http://www.cisco.com/warp/public/707/cisco-sa-20080213-phone.shtml

Affected Products
=================

Vulnerable Products
+------------------

The following Cisco Unified IP Phone devices running Skinny Client
Control Protocol (SCCP) firmware:

* 7906G
* 7911G
* 7935
* 7936
* 7940
* 7940G
* 7941G
* 7960
* 7960G
* 7961G
* 7970G
* 7971G

The following Cisco Unified IP Phone devices running Session
Initiation Protocol (SIP) firmware:

* 7940
* 7940G
* 7960
* 7960G

The version of firmware running on an IP Phone can be determined via
the Settings menu on the phone or via the phone HTTP interface.

Products Confirmed Not Vulnerable
+--------------------------------

No other Cisco products are known to be vulnerable. This includes the
following Cisco Unified IP Phone devices:

* 7931
* 7937
* 7942
* 7945
* 7965
* 7975

Details
=======

SCCP and SIP-Related Vulnerabilities

* DNS Response Parsing Overflow

Cisco Unified IP Phone 7940, 7940G, 7960 and 7960G devices
running SCCP and SIP firmware contain a buffer overflow
vulnerability in the handling of DNS responses. A
specially-crafted DNS response may be able to trigger a buffer
overflow and execute arbitrary code on a vulnerable phone. This
vulnerability is corrected in SCCP firmware version 8.0(8) and
SIP firmware version 8.8(0). This vulnerability is documented in
CVE-2008-0530 leavingcisco.com and Cisco Bug IDs CSCsj74818 and
CSCsk21863.

SCCP-Only Related Vulnerabilities

* Large ICMP Echo Request DoS

Cisco Unified IP Phone 7940, 7940G, 7960 and 7960G devices
running SCCP firmware contain a DoS vulnerability. It is possible
to cause a vulnerable device to reboot by sending a large ICMP
echo request packet. This vulnerability is corrected in SCCP
firmware version 8.0(6). This vulnerability is documented in
CVE-2008-0526 leavingcisco.com and Cisco Bug ID CSCsh71110.

* HTTP Server DoS

Cisco Unified IP Phone 7935 and 7936 devices running SCCP
firmware contain a DoS vulnerability in their internal HTTP
server. By sending a specially crafted HTTP request to TCP port
80 on a vulnerable phone, it may be possible to cause the phone
to reboot. It is possible to workaround this issue by disabling
the internal HTTP server on vulnerable phones. The internal HTTP
server only listens to TCP port 80. This vulnerability is
corrected in SCCP firmware version 3.2(17) for 7935 devices and
SCCP firmware version 3.3(15) for 7936 devices. This
vulnerability is documented in CVE-2008-0527 leavingcisco.com and
Cisco Bug ID CSCsk20026.

* SSH Server DoS

Cisco Unified IP Phone 7906G, 7911G, 7941G, 7961G, 7970G and
7971G devices running SCCP firmware contain a buffer overflow
vulnerability in their internal Secure Shell (SSH) server. By
sending a specially crafted to packet to TCP port 22 on a
vulnerable phone, it may be possible for an unauthenticated
attacker to cause the phone to reboot. It may also be possible
for an unauthenticated attacker to execute arbitrary code with
system privileges. It is possible to workaround this issue by
disabling the internal SSH server on vulnerable phones. The
internal SSH server only listens to TCP port 22. This
vulnerability is corrected in SCCP firmware version 8.2(2)SR2.
This vulnerability is documented in CVE-2004-2486
leavingcisco.com and Cisco Bug ID CSCsh79629.

SIP-Only Related Vulnerabilities

* SIP MIME Boundary Overflow

Cisco Unified IP Phone 7940, 7940G, 7960 and 7960G devices
running SIP firmware contain a buffer overflow vulnerability in
the handling of Multipurpose Internet Mail Extensions (MIME)
encoded data. By sending a specially crafted SIP message to a
vulnerable phone, it may be possible to trigger a buffer overflow
and execute arbitrary code on the phone. This vulnerability is
corrected in SIP firmware version 8.8(0). This vulnerability is
documented in CVE-2008-0528 leavingcisco.com and Cisco Bug ID
CSCsj74786.

* Telnet Server Overflow

Cisco Unified IP Phone 7940, 7940G, 7960 and 7960G devices
running SIP firmware contain a buffer overflow vulnerability in
their internal telnet server. The telnet server is disabled by
default and can be configured to allow either privileged or
unprivileged user-level access. If the telnet server is enabled
for privileged or unprivileged access, the phone password
parameter must additionally be configured to permit telnet
access. By entering a specially crafted command on a phone
configured to permit unprivileged access, it may be possible for
an unprivileged-level, authenticated user to trigger a buffer
overflow and obtain privileged-level access to the phone. It is
possible to workaround this issue by disabling the internal
telnet server on vulnerable phones. This vulnerability is
corrected in SIP firmware version 8.8(0). This vulnerability is
documented in CVE-2008-0529 leavingcisco.com and Cisco Bug ID
CSCsj78359.

* SIP Proxy Response Overflow

Cisco Unified IP Phone 7940, 7940G, 7960 and 7960G devices
running SIP firmware contain a heap overflow vulnerability in the
handling of a challenge/response message from a SIP proxy. If an
attacker controls the SIP proxy to which a vulnerable phone is
registered, attempts to register, or the attacker can act as a
man-in-the-middle, it may be possible to send a malicious
challenge/response message to a phone and execute arbitrary code.
This vulnerability is corrected in SIP firmware version 8.8(0).
This vulnerability is documented in CVE-2008-0531
leavingcisco.com and Cisco Bug ID CSCsj74765.

Vulnerability Scoring Details
=============================

Cisco is providing 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.

Cisco will provide a base and temporal score. Customers can then
compute environmental scores to assist in determining the impact of
the vulnerability in individual networks.

CVSS is a standards based scoring method that conveys vulnerability
severity and helps determine urgency and priority of response.

Cisco has provided an FAQ to answer additional questions regarding
CVSS at:

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html

Cisco has also provided a CVSS calculator to help compute the
environmental impact for individual networks at:

http://intellishield.cisco.com/security/alertmanager/cvss

CSCsj74818 - DNS Response Parsing Stack Overflow

CVSS Base Score - 10.0
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - Complete
Integrity Impact - Complete
Availability Impact - Complete

CVSS Temporal Score - 8.3
Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed

CSCsk21863 - DNS Response Parsing Stack Overflow

CVSS Base Score - 10.0
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - Complete
Integrity Impact - Complete
Availability Impact - Complete

CVSS Temporal Score - 8.3
Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed

CSCsh71110 - 7940/7960 IP Phone ICMP Denial of Service

CVSS Base Score - 7.8
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete

CVSS Temporal Score - 6.4
Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed

CSCsk20026 - IP Phone HTTP Vulnerability

CVSS Base Score - 7.8
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - None
Integrity Impact - None
Availability Impact - Complete

CVSS Temporal Score - 6.4
Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed

CSCsh79629 - TNP Phone SSH Vulnerability

CVSS Base Score - 10.0
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - Complete
Integrity Impact - Complete
Availability Impact - Complete

CVSS Temporal Score - 8.3
Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed

CSCsj74786 - SIP Mime Boundary Overflow

CVSS Base Score - 10.0
Access Vector - Network
Access Complexity - Low
Authentication - None
Confidentiality Impact - Complete
Integrity Impact - Complete
Availability Impact - Complete

CVSS Temporal Score - 8.3
Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed

CSCsj78359 - SIP 40/60:Telnet access stack overflow

CVSS Base Score - 8.5
Access Vector - Network
Access Complexity - Medium
Authentication - Single
Confidentiality Impact - Complete
Integrity Impact - Complete
Availability Impact - Complete

CVSS Temporal Score - 7
Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed

CSCsj74765 - SIP Proxy Response Overflow

CVSS Base Score - 7.3
Access Vector - Network
Access Complexity - High
Authentication - None
Confidentiality Impact - Complete
Integrity Impact - Complete
Availability Impact - Complete

CVSS Temporal Score - 6.3
Exploitability - Functional
Remediation Level - Official-Fix
Report Confidence - Confirmed

Impact
======

Successful exploitation of these vulnerabilities may cause vulnerable
IP phone devices to reboot which will interrupt client voice services
and, in some cases, allow the execution of arbitrary code.

Software Versions and Fixes
===========================

When considering software upgrades, also consult
http://www.cisco.com/go/psirt and any subsequent advisories to
determine exposure and a complete upgrade solution.

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 assistance.

Workarounds
===========

Workarounds are available for several of the vulnerabilities.
Disabling unnecessary internal phone Telnet and HTTP servers will
eliminate exposure to the Telnet Server overflow and HTTP Server DoS
vulnerabilities.

It is possible to mitigate these vulnerabilities with access control
lists (ACL). Filters that deny ICMP Echo Request, TCP port 22 (SSH),
TCP port 23 (Telnet), TCP port 80 (HTTP), TCP/UDP port 53 (DNS) and
TCP/UDP port 5060 (SIP) should be deployed at voice/data network
boundaries as part of a tACL policy for protection of traffic which
enters the network at ingress access points. This policy should be
configured to protect the network device and other devices behind it
where the filter is applied.

Additional information about tACLs is available in "Transit Access
Control Lists: Filtering at Your Edge":

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_white_paper09186a00801afc76.shtml

Additional mitigation techniques that can be deployed on Cisco
devices within the network are available in the Cisco Applied
Mitigation Bulletin companion document for this advisory:

http://www.cisco.com/warp/public/707/cisco-amb-20080116-phone.shtml

Obtaining Fixed Software
========================

Cisco will make free software available to address this vulnerability
for affected customers. This advisory will be updated as fixed
software becomes available. 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 a
http://www.cisco.com/public/sw-license-agreement.html , or as otherwise
set forth at Cisco.com Downloads at
http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact either "psirt@xxxxxxxxx" or "security-alert@xxxxxxxxx"
for software upgrades.

Fixed Firmware for SCCP-Related Vulnerabilities

For the Large ICMP Echo DoS, fixed SCCP firmware version 8.0(6) and
later for Cisco Unified IP Phone 7940, 7940G, 7960 and 7960G devices
is available.

For the HTTP Server DoS, fixed SCCP firmware version 3.2(17) and
later for Cisco Unified IP Phone 7935 devices and fixed SCCP firmware
3.3(15) and later for Cisco Unified IP Phone 7936 devices are
available.

For the SSH Server DoS, fixed SCCP firmware version 8.2(2)SR2 and
later for Cisco Unified IP Phone 7906G, 7911G, 7941G, 7961G, 7970G
and 7971G devices is available.

For the DNS Response Parsing overflow, fixed SCCP firmware version
8.0(8) and later for Cisco Unified IP Phone 7940, 7940G, 7960 and
7960G devices is available.

Fixed firmware for all SCCP-related vulnerabilities can be obtained
here:

http://www.cisco.com/pcgi-bin/tablebuild.pl/ip-7900ser?psrtdcat20e2

Fixed Firmware for SIP-Related Vulnerabilities

All the SIP-related vulnerabilities referenced in this advisory are
fixed in SIP firmware version 8.0(6) and later for Cisco Unified IP
Phone 7940, 7940G, 7960 and 7960G devices, which can be obtained
here:

http://www.cisco.com/pcgi-bin/tablebuild.pl/sip-ip-phone7960?psrtdcat20e2

Customers with Service Contracts
+-------------------------------

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 http://www.cisco.com.

Customers using Third Party Support Organizations
+------------------------------------------------

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 without Service Contracts
+----------------------------------

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 at obtaining fixed software through
their point of sale should get their upgrades 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)
* e-mail: tac@xxxxxxxxx

Have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free
upgrades for non-contract customers must be requested through the
TAC.

Refer to http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml
for additional TAC contact information, including special localized
telephone numbers and instructions and e-mail addresses for use in
various languages.

Exploitation and Public Announcements
=====================================

The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerabilities described in this advisory.

The SIP MIME Boundary, Telnet Server, DNS Response Parsing and SIP
Proxy Response overflows were reported to Cisco by Jon Griffin and
Mustaque Ahamad of the School of Computer Science at the Georgia
Institute of Technology.

The HTTP Server DoS was reported to Cisco by Sven Weizenegger of
T-Systems.

The Large ICMP Echo Request DoS vulnerability was reported to Cisco
by a customer. The SSH Server DoS was discovered internally by Cisco.

Status of this Notice: FINAL
============================

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.

Distribution
============

This advisory is posted on Cisco's worldwide website at:

http://www.cisco.com/warp/public/707/cisco-sa-20080213-phone.shtml

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.

* cust-security-announce@xxxxxxxxx
* first-teams@xxxxxxxxx
* bugtraq@xxxxxxxxxxxxxxxxx
* vulnwatch@xxxxxxxxxxxxx
* cisco@xxxxxxxxxxxxxxxxx
* cisco-nsp@xxxxxxxxxxxxxxx
* full-disclosure@xxxxxxxxxxxxxxxxx
* comp.dcom.sys.cisco@xxxxxxxxxxxxxxxxxx

Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on
mailing lists or newsgroups. Users concerned about this problem are
encouraged to check the above URL for any updates.

Revision History
================

+----------------------------------------+
| Revision | | Initial |
| 1.0 | 2008-February-13 | public |
| | | release. |
+----------------------------------------+

Cisco Security Procedures
=========================

Complete information on reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and
registering to receive security information from Cisco, is available
on Cisco's worldwide website at:

http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html

This includes instructions for press inquiries regarding Cisco
security notices. All Cisco security advisories are available at:

http://www.cisco.com/go/psirt
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