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Cisco Security Advisory:
Unintentional Password Modification in Cisco Firewall Products
Document ID: 70811
Advisory ID: cisco-sa-20060823-firewall
http://www.cisco.com/warp/public/707/cisco-sa-20060823-firewall.shtml
Revision 1.0
For Public Release 2006 August 23 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
=======
Certain versions of the software for the Cisco PIX 500 Series Security
Appliances, the Cisco ASA 5500 Series Adaptive Security Appliances
(ASA), and the Firewall Services Module (FWSM) are affected by a
software bug that may cause the EXEC password, passwords of locally
defined usernames, and the enable password in the startup configuration
to be changed without user intervention.
Unauthorized users can take advantage of this bug to try to gain access
to a device that has been reloaded after passwords in its startup
configuration have been changed. In addition, authorized users can be
locked out and lose the ability to manage the affected device.
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-20060823-firewall.shtml.
Affected Products
=================
Cisco PIX 500 Series Security Appliances, the Cisco ASA 5500 Series
Adaptive Security Appliances, and the Firewall Services Module (FWSM)
for the Cisco Catalyst 6500 Switches and Cisco 7600 Series Routers are
impacted if they are running an affected software version.
Vulnerable Products
+------------------
The PIX 500 Series Security Appliances and the ASA 5500 Series Adaptive
Security Appliances are affected when running any of the following
software versions:
* Any version (including interim versions) in the 7.0(x) train up to
and including 7.0(5)
* Any version (including interim versions) in the 7.1(x) train up to
and including 7.1(2.4)
The FWSM for the Cisco Catalyst 6500 Switches and Cisco 7600 Series
Routers is affected when running the following software version:
* Any version (including interim versions) in the 3.1(x) train up to
and including 3.1(1.6)
Products Confirmed Not Vulnerable
+--------------------------------
The PIX 500 Series Security Appliances and the ASA 5500 Series Adaptive
Security Appliances are not affected when running any of the following
software versions:
* Any pre-7.x version (PIX only since the ASA does not run pre-7.x
code)
* 7.2(1) and later
The FWSM for the Cisco Catalyst 6500 Switches and Cisco 7600 Series
Routers is not affected when running any of the following software
versions:
* Any 1.x and 2.x version
* 3.1(2) and later
No other Cisco products are currently known to be affected by this
issue.
Details
=======
The Cisco PIX 500 Series Security Appliances, the Cisco ASA 5500 Series
Adaptive Security Appliances, and the Firewall Services Module (FWSM)
for the Cisco Catalyst 6500 Switches and Cisco 7600 Series Routers are
part of Cisco's security portfolio. All of these products offer
firewall services with stateful packet filtering and deep packet
inspection. The PIX and ASA devices also offer other services like
Virtual Private Networking (VPN), Content Filtering, and Intrusion
Prevention.
On these devices, authentication for both EXEC mode and enable mode can
be performed based on Authentication, Authorization, and Accounting
(AAA) methods (Remote Authentication Dial-In User Service [RADIUS],
Terminal Access Controller Access Control System Plus [TACACS+], or
LOCAL). If a device does not have any AAA method (i.e., RADIUS,
TACACS+, or LOCAL) configured, authentication for EXEC mode is
performed using the password configured with the "passwd" command, and
authentication for enable mode is performed using the password
configured with the "enable password" command.
A software bug exists in certain versions of the software used by these
devices that may cause, under some circumstances, the EXEC password,
passwords of locally defined users, and the enable password that are
stored in the startup configuration to be changed without user
intervention. The startup configuration is stored in a non-volatile
medium such as flash memory.
The affected passwords are set using the following configuration
commands:
* passwd - configures the EXEC password. For example:
pix(config)# passwd xxxxxxxxx
* username - configures local users and their associated passwords.
For example:
pix(config)# username admin password xxxxxxxx
* enable password - configures the password used to enter enable
mode. For example:
pix(config)# enable password xxxxxxxx
The software bug is known to be triggered in only two scenarios:
* A software crash, normally caused by a software bug. Please note
that not all software crashes may cause the undesired results
discussed above.
* Two or more users making concurrent configuration changes on a
device, regardless of the method (command-line interface [CLI],
Adaptive Security Device Manager [ASDM], Firewall Management
Center, etc.) used to access the device.
Please note that the passwords in the startup configuration will be
changed when the configuration is saved, to the non-volatile medium
where the startup configuration is stored, via the "write memory" or
"copy running-config startup-config" commands. During normal
operation, if the running configuration is not saved, passwords in
the startup configuration will not change.
Once the passwords in the startup configuration are changed,
administrators will be locked out after the next device reload if
authentication for EXEC and for enable privilege depends on the
passwords or local accounts stored in the startup configuration. If a
AAA server (RADIUS or TACACS+) is used for authentication, the change
of passwords in the startup configuration will only cause the undesired
results when the AAA server is unavailable, regardless of whether the
"LOCAL" authentication method is configured as a fallback, e.g. aaa
authentication enable console RADIUS LOCAL.
Passwords are changed to a non-random value. This behavior is not due
to a hardcoded default password or other explicitly induced set of
password values, but rather the result of a coding error related to
configuration parsing.
Devices configured in multiple context mode are also affected by this
software bug.
This issue is documented in the following Cisco bug IDs:
* CSCse02703 for the PIX and ASA devices
* CSCsd81487 for the FWSM
Impact
======
The software issue may cause the EXEC password, password of locally
defined users, and the enable password in the startup configuration to
change without user's intervention. This will prevent administrators
from logging in to the device if authentication is configured to use
the passwords stored in the startup configuration.
If a malicious user were able to guess the new password, and the device
reloads, either automatically because of a software crash, or manually
by the network administrator, unauthorized access to the device may be
possible.
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.
For version 7.0.x of the PIX/ASA software, the first fixed release is
7.0(5.1). The latest 7.0.x release for the PIX can be downloaded from:
http://www.cisco.com/pcgi-bin/tablebuild.pl/pix?psrtdcat20e2
The latest 7.0.x release for the ASA can be downloaded from:
http://www.cisco.com/pcgi-bin/tablebuild.pl/asa?psrtdcat20e2
For version 7.1.x of the PIX/ASA software, the first fixed release is
7.1(2.5). The latest 7.1.x interim for the PIX can be downloaded from:
http://www.cisco.com/pcgi-bin/tablebuild.pl/pix-interim?psrtdcat20e2
The latest 7.1.x interim for the ASA can be downloaded from:
http://www.cisco.com/pcgi-bin/tablebuild.pl/asa-interim?psrtdcat20e2
The first fixed release of the FWSM is 3.1(2). The latest 3.1 release
of the FWSM software can be downloaded from:
http://www.cisco.com/pcgi-bin/tablebuild.pl/cat6000-fwsm?psrtdcat20e2
Note: Interim images are not fully regression tested. Each individual
fix has been unit tested, and the image has had a limited amount of
automated regression testing to confirm a baseline of functionality.
Keep this testing status in mind if you decide to run them in a
production environment. We strongly encourage you to upgrade to a fully
tested Maintenance or Feature release when it becomes available.
Workarounds
===========
Configuring authentication against an external RADIUS/TACACS+ server,
per network security best practices, mitigates this issue. For
information on how to configure authentication, please visit the
following URLs:
PIX/ASA: http://www.cisco.com/univercd/cc/td/doc/product/multisec/asa_sw/v_70/config/aaa.htm
FWSM: http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/mod_icn/fwsm/fwsm_3_1/fwsm_cfg/aaa_f.htm
If the passwords in the startup configuration have been modified as a
result of software crash or concurrent configuration update, the
administrators will need to perform a password recovery procedure,
unless external AAA authentication is configured.
The password recovery procedure for the PIX and the ASA is documented
at the following URL:
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_password_recovery09186a008009478b.shtml
The password recovery procedure for the FWSM is documented at the
following URL:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/mod_icn/fwsm/fwsm_3_1/fwsm_cfg/troubl_f.htm#wp1049302
In addition, it is possible to limit the exposure of the firewall
device by permitting remote connections only from known, trusted IP
addresses. This is accomplished via the "ssh", "telnet", and "http" commands
for Secure Shell (SSH), Telnet, and Secure Hyper-Text Transfer Protocol
(HTTPS) access, respectively. For additional information on this,
please refer to the "Managing System Access" section of the Cisco
Security Appliance CLI Configuration Guide, available at:
http://www.cisco.com/univercd/cc/td/doc/product/multisec/asa_sw/v_70/config/mgaccess.htm
In the case of the FWSM, please note that remote access to it can also
be obtained via the Cisco Catalyst 6500 switch or Cisco 7600 Series
router that hosts the FWSM blade. For this reason, the switch or router
needs to be configured, using access control lists, to permit remote
connections only from known, trusted IP addresses.
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 at
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@private" or "security-alert@private"
for software upgrades.
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@private
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 issue described in this advisory, although we are aware that
some customers have been impacted by this software bug.
This issue was brought to Cisco's attention by Terje Bless from Helse
Nord IKT. Cisco would like to thank him for working with us towards
coordinated disclosure of this issue.
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-20060823-firewall.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@private
* first-teams@private
* bugtraq@private
* vulnwatch@private
* cisco@private
* cisco-nsp@private
* full-disclosure@private
* comp.dcom.sys.cisco@private
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 | 2006-August-23 | 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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All contents are Copyright 1992-2006 Cisco Systems, Inc. All rights
reserved.
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Updated: Aug 23, 2006 Document ID: 70811
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