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Cisco Security Advisory:
Cisco Router Web Setup Ships with Insecure Default IOS Configuration
Document ID: 70650
Advisory ID: cisco-sa-20060712-crws
http://www.cisco.com/warp/public/707/cisco-sa-20060712-crws.shtml
Revision 1.0
For Public Release 2006 July 12 1600 UTC (GMT)
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Contents
=======
Summary
Affected Products
Details
Impact
Software Version and Fixes
Workarounds
Obtaining Fixed Software
Exploitation and Public Announcements
Status of this Notice: FINAL
Distribution
Revision History
Cisco Security Procedures
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Summary
======
The default Cisco IOS configuration shipped with the Cisco Router Web
Setup (CRWS) application allows the execution of commands at privilege
level 15 through the Cisco IOS HTTP (Hypertext Transfer Protocol)
server web interface without requiring authentication credentials.
Privilege level 15 is the highest privilege level on Cisco IOS?
devices.
Fixed versions of the CRWS application have been modified by Cisco to
provide a more secure default IOS configuration and additional
functionality with regards to the Cisco IOS HTTP server web interface.
This issue does not require a Cisco IOS software upgrade or a CRWS
software upgrade. Customers who decide to upgrade to a fixed version of
CRWS and deploy the new default IOS configuration will not need to
deploy the suggested workarounds. Customers who elect NOT to upgrade to
a fixed CRWS version, or customers upgrading to a fixed CRWS version
who keep their existing configuration should implement the workarounds
identified in this advisory.
Additional information on the new default IOS configuration shipped
with the CRWS application is available in the Details section of this
advisory.
This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-20060712-crws.shtml.
Affected Products
================
Vulnerable Products
+------------------
The following Cisco routers whose configurations have been based on the
default IOS configuration shipped with any version of CRWS prior to
version 3.3.0 build 31 may be affected by this vulnerability:
* Cisco 806
* Cisco 826
* Cisco 827
* Cisco 827H
* Cisco 827-4v
* Cisco 828
* Cisco 831
* Cisco 836
* Cisco 837
* Cisco SOHO 71
* Cisco SOHO 76
* Cisco SOHO 77
* Cisco SOHO 77H
* Cisco SOHO 78
* Cisco SOHO 91
* Cisco SOHO 96
* Cisco SOHO 97
Products Confirmed Not Vulnerable
+--------------------------------
Any of the previously listed Cisco routers whose IOS configuration is
not based on the default IOS configuration shipped with the CRWS
application are not vulnerable.
No other Cisco products are currently known to be affected by this
vulnerability.
Details
======
The Cisco Router Web Setup tool (CRWS) provides a graphical user
interface (GUI) for configuring Cisco SOHO and Cisco 800 series
routers, and allows users to set up their routers quickly and easily.
The GUI is accessed through the Cisco IOS HTTP server, which is enabled
on the default IOS configuration shipped with the CRWS application.
The Cisco IOS HTTP server uses the "enable password" (assuming one has
been configured) as its default authentication mechanism. Other
authentication mechanisms can be configured, including the use of a
local user database, an external RADIUS (Remote Authentication Dial In
User Service) or an external TACACS+ (Terminal Access Controller Access
Control System) server. The default IOS configuration shipped with the
CRWS application does not include an "enable password" or an "enable
secret" command, allowing access to the Cisco IOS HTTP server interface
at any privilege level, up to and including privilege level 15, without
providing authentication credentials. Privilege level 15 is the highest
privilege level on Cisco IOS devices.
To resolve this vulnerability, Cisco has made changes to the default
IOS configuration shipped with the CRWS application and to the CRWS
application itself. Those changes are as follows:
* The addition of a default username and password combination to be
used during initial device configuration.
Note: CRWS will prompt the user to change those default
credentials during its first invocation. It is strongly recommended
for customers to remove those default credentials from the device
configuration by using the Cisco IOS CLI (command line interface)
if not planning to use the CRWS application for device
configuration.
* The addition of an authentication mechanism for the Cisco IOS HTTP
server to authenticate users based on the local user database.
* The addition of an access restriction to only allow connections to
the Cisco IOS HTTP server from the internal network, using the
addressing schema from the default IOS configuration shipped with
CRWS.
* The addition of a login banner, displayed on connections to the
device through Telnet or the console port, reminding users to
remove the default credentials.
* The addition of an authentication mechanism to the console port to
authenticate users based on the local user database.
* A modification to the CRWS application to force users to change the
default credentials the first time they access the CRWS GUI.
* A modification to the CRWS application to allow users to enable or
disable access to the IOS HTTP server interface from the public
interface.
This vulnerability is documented by the following Cisco bug ID:
* CSCsa78190
Note: Implementation of the available workarounds require manual
configuration to mitigate the impact of this vulnerability for existing
CRWS customers, even if upgrading to a fixed version of software.
Devices using CRWS for configuration and management are affected by
this vulnerability if the following conditions are met:
* The current device configuration is based on the default IOS
configuration shipped with the CRWS application, and
* the Cisco IOS HTTP server, which is enabled in the default IOS
configuration shipped with CRWS, has not been disabled by the user,
and
* no additional authentication mechanism (for example, local user
database, RADIUS, TACACS+) has been defined for access to the IOS
HTTP server, or no "enable password" or "enable secret" is present in
the configuration.
The following procedure can be used to determine if a given device is
vulnerable:
1. Is the Cisco IOS HTTP server enabled on the device?
* YES - Proceed to step 2.
* NO - The device is not vulnerable.
2. Is there an authentication mechanism configured for access to the
IOS HTTP server interface?
* YES - The device is not vulnerable.
* NO - Proceed to step 3.
3. Is there an "enable password" or an "enable secret" configured on the
device?
* YES - The device is not vulnerable.
* NO - The device is vulnerable. Please read the Software Versions and
Fixes section and the Workarounds sections of this security
advisory.
The following step-by-step procedure can be used in order to obtain the
information needed to answer the questions in the previous procedure:
1. In order to determine if the Cisco IOS HTTP server is enabled on
the device, execute the following command from a privileged CLI
prompt:
show running-config | include ip http
The following example shows a device on which the Cisco IOS HTTP
server is enabled:
Router#show running-config | include ip http
ip http server
Router#
The following example shows a device on which the Cisco IOS HTTP
server is disabled:
Router#show running-config | include ip http
no ip http server
Router#
Note: Newer versions of the Cisco IOS HTTP server provide SSL
(Secure Sockets Layer) encryption. This vulnerability can also be
exploited if the SSL-enabled Cisco IOS HTTP server is enabled on
the configuration. The following example shows a device on which
the standard Cisco IOS HTTP server is disabled, but the SSL-enabled
Cisco IOS HTTP server is enabled:
Router#show running-config | include ip http
no ip http server
ip http secure-server
Router#
2. In order to determine if an authentication mechanism has been
applied to the Cisco IOS HTTP server, execute the following command
from a privileged CLI prompt:
show running-config | include ip http
The following example shows a device on which the Cisco IOS HTTP
server is enabled and the local authentication mechanism has been
configured:
Router#show running-config | include ip http
ip http server
ip http authentication local
no ip http secure-server
Router#
The absence of an "ip http authentication" line on the device
configuration implies that the Cisco IOS HTTP server will use the
"enable secret" or "enable password" (if so configured) as the
authentication mechanism. Additional information on AAA mechanisms
available for the Cisco IOS HTTP server can be found in the
document entitled "AAA Control of the IOS HTTP Server", available at
http://www.cisco.com/en/US/tech/tk59/technologies_tech_note09186a008069bdc5.shtml .
3. In order to determine if an "enable password" or "enable secret" has
been configured, execute the following command from a privileged
CLI prompt:
show running-config | include enable [secret|password]
The following example shows a device on which an "enable secret"
password has been configured:
Router#show running-config | include enable [secret|password]
enable secret 5 $1$1yfp$qM7qAChXVXYp8ee2qm2Kf/
Router#
The following example shows a device on which no "enable password" or
"enable secret" has been configured:
Router#show running-config | include enable [secret|password]
Router#
Impact
=====
Successful exploitation of this vulnerability may allow for the
execution of commands on the device at any privilege level, up to and
including privilege level 15. Accessing the device at privilege level
15 would enable total control of the device, including but not limited
to device configuration changes and device reloading.
Software Version 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.
This issue is fixed for new installations in CRWS version 3.3.0 build
31, which is available at
http://www.cisco.com/pcgi-bin/tablebuild.pl/crws
Information about how to install CRWS version 3.3.0 build 31 can be
found at
http://www.cisco.com/en/US/products/sw/netmgtsw/ps2076/prod_troubleshooting_guide09186a0080132c3c.html#1080818
Existing CRWS users or customers upgrading to CRWS version 3.3.0 build
31 from any previous version should deploy the workarounds mentioned in
the Workarounds section of this security advisory. Upgrading the CRWS
software on the device from a previous version to a fixed software
version will not eliminate the vulnerability for existing
installations.
Workarounds
==========
There are multiple workarounds to mitigate this vulnerability. Existing
CRWS customers, and customers upgrading to a new CRWS version from a
previous one, should deploy one of the following workarounds if
vulnerable to this issue. Upgrading to a new CRWS version is not enough
to eliminate this vulnerability.
* Workaround 1 - Disabling the Cisco IOS HTTP Server Functionality
Customers not using the CRWS application to configure or manage
their devices and not needing the functionality provided by the
Cisco IOS HTTP server can disable it by adding the following
commands to their device configuration:
no ip http server
no ip http secure-server
The second command might return an error message if the Cisco IOS
version installed and running on the device does not support the
SSL functionality. This error message is harmless and can be safely
ignored.
* Workaround 2 - Enabling Authentication of Requests to the Cisco IOS
HTTP Server by Configuring an Enable Password
Customers using the CRWS application to configure or manage their
devices, or requiring the functionality provided by the Cisco IOS
HTTP server must configure an authentication mechanism for access
to the Cisco IOS HTTP server interface. One of those options is to
configure an "enable secret" or "enable password" password. The "enable
password" is the default authentication mechanism used by the Cisco
IOS HTTP server if no other method has been configured.
In order to configure an "enable secret" password, add the following
command to the device configuration:
enable secret