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Cisco Security Advisory: Cisco IronPort Appliances Telnet Remote Code Execution Vulnerability

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Cisco Security Advisory: Cisco IronPort Appliances Telnet Remote Code
Execution Vulnerability

Advisory ID: cisco-sa-20120126-ironport

Revision 1.0

For Public Release 2012 January 26 17:00  UTC (GMT)

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

Summary
=======

Cisco IronPort Email Security Appliances (ESA) and Cisco IronPort
Security Management Appliances (SMA) contain a vulnerability that may
allow a remote, unauthenticated attacker to execute arbitrary code
with elevated privileges.

Workarounds that mitigate this vulnerability are available.

This advisory is available at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120126-ironport

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

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

The following Cisco IronPort Email Security Appliances (ESA) and
Cisco IronPort Security Management Appliances (SMA) are affected by
this vulnerability:

    * Cisco IronPort Email Security Appliance (C-Series and X-Series)
    versions prior to 7.6.0

    * Cisco IronPort Security Management Appliance (M-Series) versions
    prior to 7.8.0


Note: Fixed software versions are not yet available.  Please consult
the Obtaining Fixed Software section of this advisory for more
information.

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

Cisco IronPort Web Security Appliances (S-Series) are not affected by
this vulnerability. 

No other Cisco products are currently known to be affected by this
vulnerability.

Details
=======

The Cisco IronPort ESA provides email management and protection
combining antispam, antivirus, encryption, digital rights management,
and archiving technologies. The Cisco IronPort SMA is a flexible
management tool designed to centralize and consolidate policy and
runtime data, providing a single management interface for multiple
Cisco IronPort security appliances.

The Cisco IronPort ESA and the Cisco IronPort SMA run AsyncOS, a
modified version of the FreeBSD kernel.

These devices are affected by the FreeBSD telnetd remote code
execution vulnerability documented by Common Vulnerabilities and
Exposures (CVE) identifier CVE-2011-4862. This vulnerability could
allow a remote, unauthenticated attacker to run arbitrary code with
elevated privileges.

The vulnerability is documented in Cisco IronPort bug 83262.

Note: Cisco IronPort tracks bugs using an internal system that is not
available to customers. The Cisco IronPort bug tracking identifiers
are provided for reference only.

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

Cisco has scored the vulnerability in this advisory based on the
Common Vulnerability Scoring System (CVSS). The CVSS scoring in this
security advisory is in accordance with CVSS version 2.0.

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

Cisco has provided a base and temporal score. Customers can also
compute environmental scores that help determine the impact of the
vulnerability in their own networks.

Cisco has provided additional information regarding CVSS at the
following link:

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

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

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


* CVE-2011-4862/Ironport #83262 ("Telnetd encrypt_keyid 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 - 9.0
    Exploitability -           Functional
    Remediation Level -        Workaround
    Report Confidence -        Confirmed


Impact
======

Successful exploitation of this vulnerability could allow a remote,
unauthenticated attacker to execute arbitrary code with elevated
privileges.

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

Fixes for the vulnerability described in this advisory are not yet
available; however, there are configuration workarounds available
that may eliminate the risk for most customers. Please see the
Workarounds section of this advisory for information on the
mitigation of this vulnerability.

Cisco IronPort Email Security Appliance (C-Series and X-Series)
versions prior to 7.6.0 are affected. Version 7.6.0 will include
fixes for this issue when available.

Cisco IronPort Security Management Appliance (M-Series) versions
prior to 7.8.0 are affected. Versions 7.8.0 and 7.9.0 will include
fixes for this issue when available.

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

By default, Telnet is configured on the Management port. Telnet
services can be disabled to mitigate this vulnerability.
Administrators can disable Telnet by using the administration
graphical user interface (GUI) or by using the "interfaceconfig"
command in the command-line interface (CLI).  As a security best
practice, customers should use Secure Shell (SSH) instead of Telnet.

Complete the following steps to disable Telnet via the GUI:

Step 1: Navigate to Network > IP Interfaces > interface_name.

Step 2: Remove the check from the box next to the Telnet service.

Step 3: Click on the Submit button to submit the change.

Step 4: Click the Commit Change button for these changes to take effect.

Use the "interfaceconfig" command, as shown in the example below to
disable Telnet via the CLI.

+-----------------------------------------------------------
mail3.example.com> interfaceconfig


Currently configured interfaces:
1. Data 1 (192.168.1.1/24 on Data1: mail3.example.com)
2. Data 2 (192.168.2.1/24 on Data2: mail3.example.com)
3. Management (192.168.42.42/24 on Management: mail3.example.com)
 
Choose the operation you want to perform:
 - NEW - Create a new interface.
 - EDIT - Modify an interface.
 - GROUPS - Define interface groups.
 - DELETE - Remove an interface.
 
[]> edit


Enter the number of the interface you wish to edit.
[]> 3

<output omitted>

Do you want to enable Telnet on this interface?  [N]> N
Do you want to enable SSH on this interface?  [N]> Y
+-----------------------------------------------------------


Note: The "interfaceconfig" command is described in detail in the
section "Other Tasks in the GUI" in the Cisco IronPort AsyncOS Daily
Management Guide available at the following link:

http://www.cisco.com/en/US/docs/security/esa/esa7.5/ESA_7.5_Daily_Management_Guide.pdf

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

Cisco Ironport has not yet released software updates that address
this vulnerability. The affected products in this advisory are
directly supported by Cisco IronPort. Customers should contact Cisco
IronPort technical support at the link below to obtain software
fixes. Cisco IronPort technical support can assist customers in
determining the correct fixes and installation procedures. Customers
should direct all warranty questions to Cisco IronPort technical
support.

Note: Do not contact psirt@xxxxxxxxx or security-alert@xxxxxxxxx for
software upgrades.

http://www.ironport.com/support/contact_support.html

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

Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, upgrades should be obtained
through the Software Center on Cisco.com at http://www.cisco.com.

Customers Using Third-Party Support Organizations
+------------------------------------------------

Customers with Cisco products that are provided or maintained through
prior or existing agreements with third-party support organizations,
such as Cisco Partners, authorized resellers, or service providers,
should contact that organization for assistance with the appropriate
course of action.

The effectiveness of any workaround or fix depends on specific
customer situations, such as product mix, network topology, traffic
behavior, and organizational mission. Because of the variety of
affected products and releases, customers should consult their
service providers or support organizations to ensure that any applied
workaround or fix is the most appropriate in the intended network
before it is deployed.

Customers Without Service Contracts
+----------------------------------

Customers who purchase directly from Cisco but do not hold a Cisco
service contract and customers who make purchases through third-party
vendors but are unsuccessful in obtaining fixed software through
their point of sale should obtain upgrades by contacting the Cisco
Technical Assistance Center (TAC):

  * +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

Customers should have the product serial number available and be
prepared to provide the URL of this advisory as evidence of
entitlement to a free upgrade. Customers without service contracts
should request free upgrades through the TAC.

Refer to Cisco Worldwide Contacts at
http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
for additional TAC contact information, including localized telephone
numbers, instructions, and e-mail addresses for support in various
languages.

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

The vulnerability in the telnetd service that affects these Cisco
IronPort appliances was publicly disclosed by the FreeBSD Project on
December 23rd, 2011. The FreeBSD Project advisory is available at: 

http://security.freebsd.org/advisories/FreeBSD-SA-11:08.telnetd.asc
 
The Cisco Product Security Incident Response Team (PSIRT) is aware of
exploit modules for the Metasploit Framework that can exploit this
vulnerability on affected Cisco IronPort appliances.

Status of This Notice: Interim
==============================

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. CISCO EXPECTS TO UPDATE THIS DOCUMENT AS NEW
INFORMATION BECOMES AVAILABLE.

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 Security Intelligence Operations at
the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120126-ironport

Additionally, a text version of this advisory is clear signed with
the Cisco PSIRT PGP key and circulated among the following e-mail
addresses:

  * cust-security-announce@xxxxxxxxx
  * first-bulletins@xxxxxxxxxxxxxxx
  * bugtraq@xxxxxxxxxxxxxxxxx
  * vulnwatch@xxxxxxxxxxxxx
  * cisco@xxxxxxxxxxxxxxxxx
  * cisco-nsp@xxxxxxxxxxxxxxx
  * full-disclosure@xxxxxxxxxxxxxxxxx

Future updates of this advisory, if any, will reside on Cisco.com but
may not be announced on mailing lists. Users can monitor this
advisory's URL for any updates.


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

+------------------------------------------------------------+
| Revision 1.0 | 2012-January-26  | Initial public release.  |
+------------------------------------------------------------+

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

Complete information about reporting security vulnerabilities in Cisco
products, obtaining assistance with security incidents, and registering
to receive security information from Cisco is available on Cisco.com at
http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html.
This web page includes instructions for press inquiries
regarding Cisco Security Advisories. All Cisco Security Advisories are
available at http://www.cisco.com/go/psirt.
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