Advisory ID: cisco-sa-20050713-ons
For Public Release 2005 July 13 15:00 UTC (GMT)
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 is posted at http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20050713-ons
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:
TID-000 98-06-20 14-30-00 M001COMPLD"VENDOR=CISCO, MODEL=SOADM-1CH-1530.33,
This output shows that ONS 15216 OADM is running software release
No other Cisco products are currently known to be affected by these
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
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
This vulnerability is documented in Cisco bug ID
-- Communications permanently lost after Telnet session closed.
Cisco has not provided scores for the vulnerability in this advisory
based on the Common Vulnerability Scoring System (CVSS). At the time of
original publication, CVSS scoring in Cisco security publications was
not yet adopted
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.
When considering software upgrades, please also consult
and any subsequent advisories to determine exposure and a complete upgrade
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.
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
Cisco has released software updates that address these vulnerabilities. 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/en/US/docs/general/warranty/English/EU1KEN_.html
, or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml
Do not contact email@example.com or firstname.lastname@example.org for software upgrades
Customers with contracts should obtain software through their regular update channels. For most customers, software patches and bug fixes should be obtained through the Software Center on Cisco's worldwide website at http://www.cisco.com
Customers whose Cisco products 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 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 who purchase direct from Cisco but do not hold a Cisco
service contract, and customers who purchase through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain software patches and bug fixes 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)
Customers should have their product serial number available and be
prepared to give the URL of this notice as evidence of entitlement to a software patch or bug fix. Customers without service contracts should request a software patch or bug fix through the TAC.
for additional TAC contact information, including localized telephone numbers,
and instructions and e-mail addresses for use in various languages.
The Cisco PSIRT is not aware of any public announcements or malicious
use of the vulnerability described in this advisory.
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.
This advisory is posted on Cisco's worldwide website at:
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.
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.
Initial public release.