Advisory ID: cisco-sa-20131023-iosxr
For Public Release 2013 October 23 16:00 UTC (GMT)
Cisco IOS XR Software Releases 3.3.0 to 4.2.0 contain a vulnerability when handling fragmented packets that could result in a denial of service (DoS) condition of the Cisco CRS Route Processor cards listed in the "Affected Products" section of this advisory.
The vulnerability is due to improper handling of fragmented packets. The vulnerability could cause the route processor, which processes the packets, to be unable to transmit packets to the fabric.
Customers that are running version 4.2.1 or later of Cisco IOS XR Software, or that have previously installed the Software Maintenance Upgrades (SMU) for Cisco bug ID CSCtz62593 are not affected by this vulnerability.
Cisco has released software updates that address this vulnerability.
This advisory is available at the following link:
This vulnerability affects Cisco IOS XR Software Releases 3.3.0 to 4.2.0 running one of the following Cisco CRS-1 Carrier Routing System (CRS) or Cisco CRS-3 route processor cards:
|Cisco CRS-1 Distributed Route Processor
||CRS-DRP-B consists of CRS-DRP-B-CPU and CRS-DRP-B-PLIM
|Cisco CRS-1 16-Slot Line-Card Chassis Route Processor
|Cisco CRS-1 8-Slot Line-Card Chassis Route Processor
|Cisco CRS-1 16-Slot Line Card Chassis Route Processor B
|Cisco CRS Series 4/8-Slot Line Card Chassis Performance Route Processor (12 GB)
|Cisco CRS Series 4/8-Slot Line Card Chassis Performance Route Processor (6 GB)
|Cisco CRS Series 16-Slot Performance Route Processor (12 GB)
|Cisco CRS Series 16-Slot Performance Route Processor (6 GB)
Note: These cards are commonly referred to as RP-A, RP-B, DRP-B, and PRP.
To determine the Cisco IOS XR Software release that is running on a Cisco product, administrators can log in to the device and issue the show version
command to display the system banner. The system banner confirms that the device is running Cisco IOS XR Software by displaying text similar to Cisco IOS XR Software
. The software version is displayed after the text "Cisco IOS XR Software".
The following example identifies a Cisco CRS series device that is running Cisco IOS XR Software Release 4.0.4:
RP/0/RP0/CPU0:CRS-G#show version | inc Cisco IOS XR Software
Fri Apr 27 22:28:14.304 UTC
Cisco IOS XR Software, Version 4.0.4[Default]
Additional information about Cisco IOS XR Software release naming conventions is available in "White Paper: Cisco IOS Reference Guide" at the following link: http://www.cisco.com/web/about/security/intelligence/ios-ref.html#9
Additional information about Cisco IOS XR Software time-based release model is available in "White Paper: Guidelines for Cisco IOS XR Software" at the following link: http://www.cisco.com/en/US/prod/collateral/iosswrel/ps8803/ps5845/product_bulletin_c25-478699.html
To determine whether a Cisco CRS series device with affected software is using a Carrier Routing System (CRS) Performance Route Processor (PRP), , Cisco Route Processor A (RP-A), or a Cisco Route Processor B (RP-B), the show inventory all
command can be issued and filtered with the product ID of the affected card. The following are examples from devices using the CRS-16-PRP-6G (PRP), CRS-16-RP-B (RP-B) and CRS-16-RP (RP-A):
RP/0/RP1/CPU0:CRS-F#show inventory all | include CRS-16-PRP
Fri Oct 11 06:59:21.384 UTC
NAME: "0/RP0/*", DESCR: "Cisco CRS Series 16 Slots 6 GB Performance Route Processor"
PID: CRS-16-PRP-6G, VID: V00, SN: -----------
NAME: "0/RP1/*", DESCR: "Cisco CRS Series 16 Slots 6 GB Performance Route Processor"
PID: CRS-16-PRP-6G, VID: V00, SN: -----------
RP/0/RP0/CPU0:CRS-A#show inventory all | include CRS-16-RP
Thu Oct 10 00:13:06.849 PDT
NAME: "0/RP0/*", DESCR: "Cisco CRS-1 Series 16 Slots Route Processor"
PID: CRS-16-RP, VID: V01, SN: -----------
NAME: "0/RP1/*", DESCR: "Cisco CRS-1 Series 16 Slots Route Processor revision B"
PID: CRS-16-RP-B, VID: V07, SN: -----------
No other Cisco products are currently known to be affected by this vulnerability, including other Route Processors such as the Cisco ASR 9000 Series RSP440, RSP-4G, and RSP-8G.
Cisco IOS XR Software Route Processor Denial of Service Vulnerability
Cisco IOS XR Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability is due to improper processing of fragmented packets by the following:
- Cisco CRS 16-Slot Line Card Chassis Route Processor (RP-A)
- Cisco CRS 16-Slot Line Card Chassis Route Processor B (RP-B)
- Carrier Routing System (CRS) Performance Route Processor (PRP)
- Cisco CRS Distributed Route Processor (DRP-B)
An attacker could exploit this vulnerability by sending fragmented packets to a vulnerable system; this vulnerability cannot be triggered by IP traffic traversing a vulnerable device. An exploit could allow the attacker to cause the packets originating on the Route Processor CPU to stop transmitting to the fabric, resulting in a DoS condition.
This vulnerability can be triggered by both IPv4 and IPv6 traffic and does not require a TCP three-way handshake.
This vulnerability has been documented in Cisco bug ID CSCuh30380
customers only) and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2013-5549
This vulnerability is addressed in the same SMU as Cisco bug ID: CSCtz62593
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:
Cisco has also provided a CVSS calculator to compute the environmental impact for individual networks at the following link:
CSCuh30380 - Cisco IOS XR Software Route Processor Denial of Service Vulnerability
Calculate the environmental score of CSCuh30380
CVSS Base Score - 7.1
CVSS Temporal Score - 5.9
Successful exploitation of the vulnerability could cause the route processor on an affected device to stop transmitting packets from the route processor CPU to the fabric. As a result, the affected RP-A, RP-B, PRP, or DRP-A will experience a DoS, failing to transmit all of its route processor-based protocols (for example, Intermediate System-to-Intermediate System, Border Gateway Protocol, ICMP).
When considering software upgrades, customers are advised to consult the Cisco Security Advisories, Responses, and Notices archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
There are no workarounds for the vulnerability described in this document.
Cisco has released software updates that address the vulnerability described in this advisory. Prior to deploying software, customers are advised to consult their maintenance providers or check the software for feature set compatibility and known issues that are specific to their environments.
Customers may only install and expect support for feature sets they have purchased. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html.
Note: This vulnerability is addressed in the same SMU as Cisco bug ID: CSCtz62593
For Cisco IOS XR Software running on the CRS Performance Route Processor, the vulnerability is present in Cisco IOS XR Software Releases 4.0.0 to 4.2.0. The following SMUs for CRS PRP series devices correct this vulnerability:
For Cisco IOS XR Software running on CRS RP-A, RP-B, or DRP-B the vulnerability is present in Cisco IOS XR Software Releases 3.3.0 to 4.2.0 inclusive for CRS-1 and Cisco IOS XR Software Releases 4.0.0 to 4.2.0 for CRS-3. The following SMUs for CRS series devices correct this vulnerability:
Cisco IOS XR Software releases prior to 3.8.0 have reached the end of software maintenance milestone. Please see: Cisco IOS XR End-of-Life and End-of-Sale Notices
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 who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through Cisco Authorized partners, resellers, and distributors (authorized 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):
- +1 800 553 2447 (toll free from within North America)
- +1 408 526 7209 (toll call from anywhere in the world)
- email: email@example.com
Customers should have the product serial number available and be prepared to provide the URL of this advisory 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.
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.
The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
This vulnerability was discovered while diagnosing issues encountered in customer networks.
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This advisory is posted on Cisco Security at the following link:
Additionally, a text version of this advisory is clear signed with the Cisco PSIRT PGP key and circulated among the following e-mail addresses:
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.
||Initial public release.