Cisco Security Advisory: SSL/TLS Certificate and SSH Public Key Validation Vulnerability
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Cisco Security Advisory:
SSL/TLS Certificate and SSH Public Key Validation Vulnerability
Advisory ID: cisco-sa-20070118-certs
http://www.cisco.com/warp/public/707/cisco-sa-20070118-certs.shtml
Revision 1.0
For Public Release 2007 January 18 1600 UTC (GMT)
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Summary
=======
The Cisco Security Monitoring, Analysis and Response System (CS-MARS)
and the Cisco Adaptive Security Device Manager (ASDM) do not validate
the Secure Sockets Layer (SSL)/Transport Layer Security (TLS)
certificates or Secure Shell (SSH) public keys presented by devices
they are configured to connect to. Malicious users may be able to use
this lack of certificate or public key validation to impersonate the
devices that these affected products connect to, which could then be
used to obtain sensitive information or misreport information.
Cisco has made free software available to address this vulnerability
for affected customers.
This advisory is posted at
http://www.cisco.com/warp/public/707/cisco-sa-20070118-certs.shtml.
Affected Products
=================
The following products are affected by the vulnerability described in
this document:
* Cisco Security Monitoring, Analysis and Response System (CS-MARS)
All CS-MARS versions prior to 4.2.3 are affected.
To verify the version of CS-MARS software, log into CS-MARS web
interface using a web browser and go to the "Help" tab located on
the top-right corner of the browser window. Then click on the
"About" link. The CS-MARS version will be displayed in the center
of the browser window under "CS-MARS Information".
Alternatively, it is possible to use an SSH connection or a direct
serial console connection to verify the version of the CS-MARS
software by logging into the system administration command line
interface with the "pnadmin" account and executing the "version"
command:
shell$ ssh pnadmin@xxxxxxxx
pnadmin@xxxxxxxx's password:
Last login: Mon Jan 8 18:42:45 2007 from 10.0.0.2
CS MARS - Mitigation and Response System
? for list of commands
[pnadmin]$ version
4.2.3 (2403)
* Cisco Adaptive Security Device Manager (ASDM)
All ASDM versions prior to 5.2(2.54) are affected when the ASDM
Launcher (the stand-alone version of ASDM) is used.
If the ASDM Applet is used, i.e. ASDM is launched via a web
browser, then it is the web browser's responsibility to verify the
certificates presented by the devices that ASDM connects to. The
user can instruct the web browser to save devices' root Certificate
Authority certificates so a warning is generated if something
changes (this can be used as a workaround - please refer to the
Workarounds section for details.)
To verify the version of ASDM software, launch ASDM and look in the
"General" tab of the "Device Information" section.
No other Cisco products are currently known to be affected by this
vulnerability.
Details
=======
Some Cisco products connect to different devices for configuration or
monitoring purposes. The actual connection method used varies depending
on the product, but SSL/TLS and SSH are the most prevalent ones due to
their use of strong cryptography to ensure the confidentiality and
integrity of the communication.
Two examples of these products include the Cisco Security Monitoring,
Analysis and Response System (CS-MARS), a security threat mitigation
system that talks to devices such as IPS sensors and firewalls, and the
Cisco Adaptive Security Device Manager (ASDM), which provides
management and monitoring services for the Cisco ASA 5500 Series
Adaptive Security Appliances, Cisco PIX 500 Series Security Appliances
and the Firewall Services Modules for the Cisco Catalyst 6500 Switches
and the Cisco 7600 Series Routers.
When these products connect to their managed devices via SSL/TLS or
SSH, they do not validate the SSL/TLS certificates or SSH public keys
presented by these managed devices.
Because the certificates and public keys presented by devices are not
validated, in the event that a certificate or public key has changed,
the affected products will not be able to determine whether the device
they are communicating with is legitimate, or if it is a device
impersonating a legitimate one.
The following Cisco Bug IDs are being used to track these
vulnerabilities on the affected products:
* CS-MARS - CSCsf95930
* ASDM - CSCsg78595
Vulnerability Scoring Details
+----------------------------
Cisco is providing scores for the vulnerabilities in this advisory
based on the Common Vulnerability Scoring System (CVSS).
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.
Cisco PSIRT will set the bias in all cases to normal. Customers are
encouraged to apply the bias parameter when determining the
environmental impact of a particular vulnerability.
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.
Cisco Bug IDs:
CSCsf95930 and CSCsg78595
CVSS Base Score: 4.7
Access Vector: Remote
Access Complexity: Low
Authentication: Not Required
Confidentiality Impact: Partial
Integrity Impact: Partial
Availability Impact: None
Impact Bias: Normal
CVSS Temporal Score: 3.9
Exploitability: Functional
Remediation Level: Official Fix
Report Confidence: Confirmed
Impact
======
Successful exploitation of this vulnerability may allow an attacker to
obtain sensitive information such as login credentials or submit false
data to the affected Cisco product by impersonating a managed device,
thus impacting the integrity of the affected Cisco product.
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 vulnerability is fixed in version 4.2.3 (2403) of the CS-MARS
software. CS-MARS software can be downloaded from the following
location:
http://www.cisco.com/pcgi-bin/tablebuild.pl/cs-mars?psrtdcat20e2
This vulnerability is fixed in version 5.2(2.54) of ASDM. ASDM can be
downloaded from the following location:
http://www.cisco.com/pcgi-bin/tablebuild.pl/asa-interim?psrtdcat20e2
Note: The ASDM versions for the PIX/ASA and the FWSM are different. A
fixed version of the ASDM software for the FWSM is forthcoming. This
advisory will be updated when a fixed image for the FWSM version of
ASDM is available.
Workarounds
===========
There are no workarounds for this vulnerability in the case of CS-MARS.
In the particular case of ASDM, using the ASDM Applet, i.e. launching
ASDM via a web browser and not via the stand-alone ASDM Launcher, will
workaround the vulnerability since the SSL/TLS certificate verification
will be performed by the web browser, and in the case that the
certificate has changed, the browser will produce a warning. Note that
this requires the user to save the root Certificate Authority (CA)
certificate as a trusted certificate.
While not a workaround for the affected products, as a security best
practice, you should always configure the devices that the affected
products connect to so only connections from trusted hosts or networks
are accepted. The way to configure this varies depending on the device.
Please refer to the documentation of your managed device for details.
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@xxxxxxxxx" or "security-alert@xxxxxxxxx"
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@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 vulnerability described in this advisory.
Cisco would like to thank Jan Bervar from NIL Data Communications for
bringing this to our attention.
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-20070118-certs.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 1.0 | 2007-January-18 | Initial public release |
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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 1992-2007 Cisco Systems, Inc. All rights
reserved.
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Updated: Jan 17, 2007 Document ID: 81583
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