A vulnerability in the egress packet processing functionality of the Cisco StarOS operating system for Cisco Aggregation Services Router (ASR) 5700 Series devices and Virtualized Packet Core (VPC) System Software could allow an unauthenticated, remote attacker to cause an interface on the device to cease forwarding packets. The device may need to be manually reloaded to clear the condition. The vulnerability is due to the failure to properly check that the length of a packet to transmit does not exceed the maximum supported length of the network interface card (NIC). An attacker could exploit this vulnerability by sending a crafted IP packet or a series of crafted IP fragments through an interface on the targeted device. A successful exploit could allow the attacker to cause the network interface to cease forwarding packets. This vulnerability could be triggered by either IPv4 or IPv6 network traffic. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180418-staros
A vulnerability in the egress packet processing functionality of the Cisco StarOS operating system for Cisco Aggregation Services Router (ASR) 5700 Series devices and Virtualized Packet Core (VPC) System Software could allow an unauthenticated, remote attacker to cause an interface on the device to cease forwarding packets. The device may need to be manually reloaded to clear the condition.
The vulnerability is due to the failure to properly check that the length of a packet to transmit does not exceed the maximum supported length of the network interface card (NIC). An attacker could exploit this vulnerability by sending a crafted IP packet or a series of crafted IP fragments through an interface on the targeted device. A successful exploit could allow the attacker to cause the network interface to cease forwarding packets. This vulnerability could be triggered by either IPv4 or IPv6 network traffic.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180418-staros
This vulnerability affects the following Cisco products when they are running the StarOS operating system and a virtual interface card is installed on the device:
To determine whether a virtual interface card is installed on the ASR 5700 Series device or VPC-SI or VPC-DI, administrators can issue the show support details | grep 'Cisco VIC' command at the device CLI.
staros# show support details | grep 'Cisco VIC'
2017-Oct-25+02:07:52.813 card 6-cpu0: <6>[ 10.967629] enic: Cisco VIC Ethernet NIC Driver, ver 2.1.1.39
Determining the StarOS Software Release
To determine whether a vulnerable release of StarOS is running on an ASR 5700 Series device, administrators can issue the show version command at the device CLI. The following example shows the output of the command for a Cisco ASR 5500 Series Router that is running Cisco StarOS Release 19.2.1:
[local]ASR-2# show version
Friday August 12 13:17:31 AST 2016
Active Software:
Image Version: 19.2.1
Image Build Number: 62564
Image Description: Deployment_Build
Image Date: Thu Dec 31 20:13:39 EST 2015
Boot Image: /flash/asr5500-19.2.1.bin
To determine whether a vulnerable release of Cisco StarOS is running on a VPC-SI or VPC-DI, administrators can issue the show version command at the device CLI. The following example shows the output of the command for a VPC-DI that is running Cisco StarOS Release 20.1.v0 (VPC-DI Release N4.6):
[local]VPC-DI# show version
Active Software:
Image Version: 20.1.v0
Image Build Number: 64657
Image Description: Deployment_Build
Image Date: Wed Jul 27 18:46:53 EDT 2016
Boot Image: /flash/qvpc-di-20.1.v0.bin
No other Cisco products are currently known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect the following Cisco products:
Exploitation of this vulnerability can cause multiple line cards to show transmit drops and errors, and the error counters would continuously increase.
Vulmon
cisco# show port datalink counters
Counters for port x/y:
Line Card Virtual Ethernet Port
Rx Counter Data | Tx Counter Data
----------------------- ------------ + ----------------------- ------------
RX Unicast frames 146446868039 | TX Unicast frames 250100240151
RX Multicast frames n/a | TX Multicast frames n/a
RX Broadcast frames n/a | TX Broadcast frames n/a
RX Size 64 frames n/a | TX Size 64 frames n/a
RX Size 65 .. 127 fr n/a | TX Size 65 .. 127 fr n/a
RX Size 128 .. 255 fr n/a | TX Size 128 .. 255 fr n/a
RX Size 256 .. 511 fr n/a | TX Size 256 .. 511 fr n/a
RX Size 512 .. 1023 fr n/a | TX Size 512 .. 1023 fr n/a
RX Size 1024 .. 1522 fr n/a | TX Size 1024 .. 1522 fr n/a
RX Size > 1522 frames n/a | TX Size > 1522 frames n/a
RX Bytes OK 164943341920449 | TX Bytes OK 207391659308726
RX Bytes BAD n/a | TX Bytes BAD 416971827
RX SHORT OK n/a | TX PAUSE n/a
RX SHORT CRC n/a | TX ERR 4083841
The presence of the transmit drops and errors could cause network traffic to cease being forwarded. If these conditions are observed, contact the Cisco Technical Assistance Center (TAC) to determine whether the device has been compromised by exploitation of this vulnerability.
Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license: http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html
Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.
When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to upgrade 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.
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 TAC: http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
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.
Fixed Releases
Customers should upgrade to an appropriate fixed release as indicated in the applicable table in this section. In the following table, the first column lists major releases of the Cisco StarOS and VPC System Software and the second column indicates the first corresponding release that includes the fix for this vulnerability.
| Cisco VPC (StarOS Major Release) | First Fixed Release |
|---|---|
| N4.0 (19.2) |
Affected; migrate to N5.1.9 (21.1.v7) |
| N4.2 (19.3) |
Affected; migrate to N5.1.9 (21.1.v7) |
| N4.5 (20.0) | Affected; migrate to N5.1.9 (21.1.v7) |
| N4.6 (20.1) | Affected; migrate to N5.1.9 (21.1.v7) |
| N4.7 (20.2) | Affected; migrate to N5.1.9 (21.1.v7) |
| N5.0 (21.0) | N5.0.4 (21.0.v4) |
| N5.1 (21.1) | N5.1.9 (21.1.v7) |
| N5.5 (21.3) | N5.5.0 (21.3.v10) |
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 found during resolution of a Cisco TAC support case.
To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
| Version | Description | Section | Status | Date |
|---|---|---|---|---|
| 1.0 | Initial public release. | - | Final | 2018-April-18 |
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