Cisco Security AdvisoryHigh
Advisory ID:
cisco-sa-20150415-iosxr
First Published:
2015 April 15 16:00 GMT
Last Updated:
2015 April 17 13:44 GMT
Version 1.1:
Workarounds:
Cisco Bug IDs:
CVSS Score:
Base 7.1,
Temporal 5.9
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AV:N/AC:M/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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AV:N/AC:M/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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A vulnerability in the packet-processing code of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers (ASR) could allow an unauthenticated, remote attacker to cause a lockup and eventual reload of a network processor chip and the line card that is processing traffic. Only Typhoon-based line cards on Cisco ASR 9000 Series Aggregation Services Routers are affected by this vulnerability.
The vulnerability is due to improper processing of packets that are routed via the bridge-group virtual interface (BVI) when any of the following features are configured: Unicast Reverse Path Forwarding (uRPF), policy-based routing (PBR), quality of service (QoS), or access control lists (ACLs). An attacker could exploit this vulnerability by sending IPv4 packets through an affected device that is configured to route them via the BVI interface. A successful exploit could allow the attacker to cause a lockup and eventual reload of a network processor chip and the line card that is processing traffic, leading to a denial of service (DoS) condition.
Cisco has released software updates that address this vulnerability. There are no workarounds to address this vulnerability.
This advisory is available at the following link:
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20150415-iosxr
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Vulnerable Products
Cisco ASR 9000 Series Routers with Typhoon-based line cards are affected by this vulnerability. To be affected by this vulnerability, the device must be configured to route traffic via the BVI and must also have any of the following features configured: uRPF, PBR, QoS, or ACLs.
This vulnerability can be exploited only with IPv4 packets that are further routed via BVI. IPv6 packets, or IPv4 packets directed to an affected device, cannot be used to trigger this vulnerability.
By default BVI, uRPF, PBR, QoS, and ACLs are not enabled in Cisco IOS XR Software.
To determine whether BVI is configured on a device, use the show running-config | include bvi privileged EXEC command. The presence of interface bvi in the output of show running-config | include bvi indicates that BVI is configured.
The following is the output of the show running-config | include bvi command on a device that is running Cisco IOS XR Software with the BVI configured:
To determine whether uRPF is enabled on an interface, use the show running-config | include verify privileged EXEC command. The presence of ipv4 verify unicast source reachable-via rx in the output of show running-config | include verify indicates that uRPF is enabled.RP/0/RSP0/CPU0:router(admin)# show running-config | include bvi
interface bvi 50
The following is the output of the show running-config | include "verify source" command on a device that is running Cisco IOS XR Software with the uRPF feature enabled:
RP/0/RSP0/CPU0:router(admin)# show running-config | include "verify source"
ipv4 verify unicast source reachable-via rx
To determine whether PBR is configured on a device, use the show running-config policy-map | include pbr privileged EXEC command. The presence of policy-map type pbr in the output of show running-config policy-map | include pbr indicates that PBR is configured.
The following is the output of the show running-config policy-map | include pbr command on a device that is running Cisco IOS XR Software with the PBR feature enabled:
To determine whether ACLs are enabled on an interface, use the show running-config | include access-group privileged EXEC command. The presence of ipv4 access-group in the output of show running-config | include access-group indicates that ACLs are configured.RP/0/RSP0/CPU0:router(admin)# show running-config policy-map | include pbr
policy-map type pbr TEST_PBR
The following is the output of the show running-config | include access-group command on a device that is running Cisco IOS XR Software with the ACL feature enabled:
RP/0/RSP0/CPU0:router(admin)# show running-config | include access-group
ipv4 access-group TEST_IN ingress
To determine whether QoS is enabled on an interface, use the show running-config | include service-policy privileged EXEC command. The presence of service-policy input or service-policy output in the output of show running-config | include service-policy indicates that QoS is configured.
The following is the output of the show running-config | include service-policy command on a device that is running Cisco IOS XR Software with the QoS feature configured:
RP/0/RSP0/CPU0:router(admin)# show running-config | include service-policy
service-policy input test_in
service-policy output test_out
The second generation of the Cisco ASR 9000 Series Ethernet line cards is referred to as Typhoon-based line cards. The term comes from the network processors (NPs) that are used on these line cards.
The following line cards are Typhoon based:
- A9K-MOD80-SE
- A9K-MOD80-TR
- A9K-MOD160-SE
- A9K-MOD160-TR
- A9K-24X10GE-SE
- A9K-24X10GE-TR
- A9K-36X10GE-SE
- A9K-36X10GE-TR
- A9K-2X100GE-SE
- A9K-2X100GE-TR
- A9K-1X100GE-SE
- A9K-1X100GE-TR
To determine whether the line card on an ASR 9000 Series Router is Typhoon based, the administrator can use the show diag command. Affected devices will include the product ID (PID) for at least one of the Typhoon-based cards. The following example shows a device on which an A9K-24X10GE-SE card is active:
RP/0/RSP0/CPU0:router(admin)# show diag
Mon Jun 22 12:55:10.554 PST
NODE module 0/RSP0/CPU0 :
MAIN: board type 0x100302
!--- output truncated
NODE module 0/1/CPU0 :
MAIN: board type 0x20207
S/N: FOC123081J6
Top Assy. Number: 68-3182-03
PID: A9K-24X10GE-SE
UDI_VID: V1D
HwRev: V0.0
New Deviation Number: 0
CLEI:
Board State : IOS XR RUN
PLD: Motherboard: N/A, Processor: 0x8004 (rev: 2.2), Power: N/A
ROMMON: Version 1.0(20081208:174521) [ASR9K ROMMON]
!--- output truncated
Note: Releases of Cisco IOS XR Software prior to 4.3.1 are not affected by this vulnerability.
Products Confirmed Not Vulnerable
Only Cisco ASR 9000 Series Routers with Typhoon-based line cards are affected by this vulnerability.
Cisco ASR 9001 and Cisco ASR 9001-S Routers are affected by this vulnerability.
Note: Releases of Cisco IOS XR Software prior to 4.3.1 are not affected by this vulnerability.
Cisco ASR 9000 Series Routers with Trident-based line cards are not affected by this vulnerability. The first generation of the ASR 9000 Series Ethernet line cards is often referred to as Trident-based line cards.
The following line cards are Trident based:
- A9K-40GE-L
- A9K-40GE-B
- A9K-40GE-E
- A9K-4T-L
- A9K-4T-B
- A9K-4T-E
- A9K-8T/4-L
- A9K-8T/4-B
- A9K-8T/4-E
- A9K-2T20GE-L
- A9K-2T20GE-B
- A9K-2T20GE-E
- A9K-8T-L
- A9K-8T-B
- A9K-8T-E
- A9K-16T/8-B
No other Cisco products are currently known to be affected by this vulnerability.
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A vulnerability in the packet-processing code of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers (ASR) could allow an unauthenticated, remote attacker to cause a lockup and eventual reload of a network processor chip and the line card that is processing traffic. Only Typhoon-based line cards on Cisco ASR 9000 Series Aggregation Services Routers are affected by this vulnerability.
The vulnerability is due to improper processing of packets that are routed via the bridge-group virtual interface (BVI) when any of the following features are configured: Unicast Reverse Path Forwarding (uRPF), policy-based routing (PBR), quality of service (QoS), or access control lists (ACLs). An attacker could exploit this vulnerability by sending IPv4 packets through an affected device that is configured to route them via the BVI interface. A successful exploit could allow the attacker to cause a lockup and eventual reload of a network processor chip and the line card that is processing traffic, leading to a denial of service (DoS) condition.
To be affected by this vulnerability, the device must be configured to route traffic via the BVI and must also have any of the following features configured: uRPF, PBR, QoS, or ACLs.
This vulnerability could be exploited repeatedly to cause an extended DoS condition.
This vulnerability has been documented in Cisco bug ID CSCur62957 (registered customers only) and has been assigned the Common Vulnerabilities and Exposures (CVE) ID CVE-2015-0695.
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There are no workarounds for this vulnerability.
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When considering software upgrades, customers are advised to consult the Cisco Security Advisories, Responses, and Alerts 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.
This vulnerability is corrected in the following Cisco IOS XR Software software maintenance updates (SMUs):
- asr9k-px-4.3.4.CSCur62957.pie for version 4.3.4
- asr9k-px-5.1.2.CSCur62957.pie for version 5.1.2
- asr9k-px-5.1.3.CSCur62957.pie for version 5.1.3
- asr9k-px-5.2.2.CSCur62957.pie for version 5.2.2
- asr9k-px-5.3.0.CSCur62957.pie for version 5.3.0
Note: Releases of Cisco IOS XR Software prior to 4.3.1 are not affected by this vulnerability.
Note: Cisco IOS XR Software SMUs for additional versions will be published when available.
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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 by Cisco TAC during the investigation of customer cases.
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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.
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Show LessRevision 1.1 2015-April-17 Modified affected releases Revision 1.0 2015-April-15 Initial public release
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