[c-nsp] Cisco Security Advisory: Cisco ONS 15216 OADM Telnet Denial-of-Service Vulnerability

Wed Jul 13 11:00:00 EDT 2005

The Cisco ONS 15216 OADM (Optical Add/Drop Multiplexer) contains a
vulnerability in the handling of telnet sessions that can cause a
denial-of-service condition in the management plane. Traffic going through the
Cisco ONS 15216 OADM (i.e. transit traffic), is not affected when the
management plane is under a denial-of-service condition. However, clearing the
denial-of-service condition on the management plane requires resetting the
device, which impacts transit traffic.

Cisco has made free software available to address this vulnerability. There are
workarounds available to mitigate the effects of the vulnerability (see the
Workarounds section).

This advisory will be posted at 
http://www.cisco.com/warp/public/707/cisco-sa-20050713-ons.shtml.

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

Vulnerable Products

Only the Cisco ONS 15216 OADM running software release 2.2.2 and earlier is
affected by the vulnerability described in this advisory.

To determine your software revision, launch a TL1 session and use the
RTRV-NE-GEN command at the TL1 prompt to retrieve the software version
information like in the following example:

    > RTRV-NE-GEN:<tid>::100;

    TID-000 98-06-20 14-30-00 M001COMPLD"VENDOR=CISCO, MODEL=SOADM-1CH-1530.33,
    SN=0001,SOFTWARE=2.0.0, SOFTWAREUPDATE=1-3-2001,FIRMWARE=1.2.7,
    FIRMWAREUPDATE=1-3-2001,CHANNUM=1,LAMBDA1=1530.33,ALM-LOSDROP-WEST-1=ON,
    ALM-LOSDROP-EAST-1=ON,NAME=SOADM-1,LONGITUDE=100,LATITUDE=45,
    IPADDRESS=10.0.0.2,IPMASK=255.0.0.0,A_POWER=OPERATING, B_POWER=OPERATING";

This output shows that ONS 15216 OADM is running software release 2.0.0.

Products Confirmed Not Vulnerable

No other Cisco products are currently known to be affected by these
vulnerabilities.

Details
=======

Telnet is a protocol used for remote management of network devices. It is
defined in RFC 854.

The Cisco ONS15216 OADMs allow service providers to add and drop single to
multiple wavelengths from their optical transport network.

The Cisco ONS 15216 OADM has separate management and data planes. The
management plane is used to manage the device and is usually connected to a
network isolated from the Internet and local to the customer's environment.
Traffic being switched and transmitted by the OADM flows through the data
plane.

Sending a specially crafted stream of data to a telnet session with the Cisco
ONS 15216 OADM can cause the session to lock up, and no further telnet sessions
can be established. While the telnet session is locked up, traffic flowing
through the data plane is not affected. Please note that a TCP session must
have been previously established, i.e. the TCP 3-way handshake must have
occurred, for the vulnerability to be triggered. This makes it difficult to
spoof the source addresses during an attack.

Restoring communications with the management plane requires reloading the Cisco
ONS 15216 OADM. This operation affects traffic flowing through the data plane.

This vulnerability is documented in Cisco bug ID CSCee23360 -- Communications
permanently lost after Telnet session closed.

Impact
======

Successful exploitation of the vulnerability described in this document may
result in a denial-of-service condition in the management plane that will
disable the remote manageability of the Cisco ONS 15216 OADM. Clearing a
denial-of-service condition on the management plane will result in a
denial-of-service condition in the data plane while the device boots up.

Software Versions and Fixes

When considering software upgrades, please also consult http://www.cisco.com/en
/US/products/products_security_advisories_listing.html 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") for assistance.

The vulnerability described in this advisory is fixed in release 2.2.3 and
later of the ONS 15216 OADM software. If you are currently running the
identified vulnerable software, you should obtain fixed software, as detailed
below.

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

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 assistance with the upgrade, which should be free of
charge.

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 at cisco.com

Please 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.

Please do not contact either "psirt at cisco.com" or "security-alert at cisco.com"
for software upgrades.

See 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.

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.

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

The effectiveness of any workaround 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 is the most appropriate for use in the intended
network before it is deployed.

The Cisco ONG platform provides separate management and data planes.
Established networking best practices recommend that the management plane is
connected to a private network that is completely isolated from the Internet
and that is not reachable by customers' traffic.

If complete management and data plane isolation is not possible it is
recommended to use Access Control Lists (ACLs) on neighboring routers to only
allow telnet connections to the Cisco ONS 15216 OADM from specific network
management stations and IP address ranges. This type of filtering could be
implemented as part of an Infrastructure ACL, which is a networking best
practice. For more information on iACLs, refer to "Protecting Your Core:
Infrastructure Protection Access Control Lists" at http://www.cisco.com/warp/
public/707/iacl.html.

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

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

Status of This Notice: FINAL

THIS ADVISORY IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF
GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF
THE INFORMATION ON THE ADVISORY OR MATERIALS LINKED FROM THE ADVISORY IS AT
YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS NOTICE AT ANY
TIME.

A stand-alone copy or paraphrase of the text of this security advisory 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 will be posted on Cisco's worldwide website at 
http://www.cisco.com/warp/public/707/cisco-sa-20050713-ons.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 at cisco.com
  * first-teams at first.org (includes CERT/CC)
  * bugtraq at securityfocus.com
  * vulnwatch at vulnwatch.org
  * cisco at spot.colorado.edu
  * cisco-nsp at puck.nether.net
  * full-disclosure at lists.grok.org.uk
  * comp.dcom.sys.cisco at newsgate.cisco.com

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  | 2005-July-13 | Initial public   |
| 1.0       |              | 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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