Advisory ID: cisco-sa-20020619-ons-tos
For Public Release 2002 June 19 15:00 UTC (GMT)
The Cisco ONS15454 optical transport platform is vulnerable when IP packets, with the Type Of Service (TOS) bit set, are sent to the Timing Control Card (TCC) LAN interface. Cisco ONS software releases 3.1.0 to 3.2.0, both inclusive, are vulnerable.
This vulnerability is documented as Cisco bug ID CSCdx48853.
Cisco has released free software updates that address these vulnerabilities.
There are workarounds available to mitigate the effects of this vulnerability.
This advisory is posted at
This section provides details on affected products.
All Cisco ONS15454 hardware running Cisco ONS release 3.1.0 to 3.2.0, both inclusive, is affected by this vulnerability.
To determine your software revision, view the help-about window on the CTC.
Hardware not affected includes the Cisco ONS15327 edge optical transport platform, Cisco ONS15540 extended service platform, ONS15800 series, ONS15200 series metro DWDM systems and the ONS15194 IP transport concentrator.
No other Cisco products are currently known to be affected by these vulnerability.
When an IP packet with non-zero TOS bits in its header is received by the TCC on its LAN interface, this causes software versions 3.1.0 and later to reset the TCC. When the crafted packets are sent repeatedly, both TCCs reset leaving no active TCC in the platform.
In order to exploit this vulnerability, an attacker must be able to establish an IP connection to the TCC's LAN interface.
This vulnerability is documented as Cisco bug ID CSCdx48853 ( registered customers only).
Cisco has not provided scores for the vulnerabilities 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.
When both TCCs are reset simultaneously, the E100 cards and E1000 cards stop passing traffic. The G1000 cards traffic would not be affected. TDM traffic may be compromised because timing is not synchronized anymore. The protection switching feature is compromised.
This vulnerability is fixed in Cisco ONS software release 3.2.1 and later.
Cisco ONS software release 3.2.1 is the maintenance release fix version for this vulnerability. Cisco ONS software version 3.3.0 is currently available as an interim fix release for this vulnerability until Cisco ONS software version 3.2.1 is released at the end of July 2002.
The procedure to upgrade to the fixed software version on the Cisco ONS 15454 is detailed at: http://www.cisco.com/univercd/cc/td/doc/product/ong/15400/r33docs/sftuprgd/index.htm.
When considering software upgrades, also consult
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.
Restrict IP traffic to the gateway node(s) with a router configured to change the TOS to zero for all out-bound packets going to the TCC.
Sample Cisco router configuration:
class-map match-all MY_LAN
!--- Matches all packets
set ip dscp default
!--- Sets all packets to "00000000" (Best effort)
service-policy output SET_TOS
!--- Modifies outbound packets
Cisco has released free 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
, or as otherwise set forth at Cisco.com Downloads at
Do not contact firstname.lastname@example.org or email@example.com for software upgrades
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
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 acquire 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: firstname.lastname@example.org
Customers should have their product serial number available and be prepared to give the URL of this notice as evidence of entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC.
Refer to http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html 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 vulnerability was reported to Cisco by Cisco customer.
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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.