A vulnerability in the Multiprotocol Label Switching (MPLS) Operations, Administration, and Maintenance (OAM) implementation of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, adjacent attacker to trigger a denial of service (DoS) condition on an affected device. The vulnerability is due to the incorrect handling of certain MPLS OAM packets. An attacker could exploit this vulnerability by sending malicious MPLS OAM packets to an affected device. A successful exploit could allow the attacker to cause the lspv_server process to crash. The crash could lead to system instability and the inability to process or forward traffic though the device, resulting in a DoS condition that require manual intervention to restore normal operating conditions. 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-20190515-iosxr-mpls-dos
A vulnerability in the Multiprotocol Label Switching (MPLS) Operations, Administration, and Maintenance (OAM) implementation of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, adjacent attacker to trigger a denial of service (DoS) condition on an affected device.
The vulnerability is due to the incorrect handling of certain MPLS OAM packets. An attacker could exploit this vulnerability by sending malicious MPLS OAM packets to an affected device. A successful exploit could allow the attacker to cause the lspv_server process to crash. The crash could lead to system instability and the inability to process or forward traffic though the device, resulting in a DoS condition that require manual intervention to restore normal operating conditions.
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-20190515-iosxr-mpls-dos
This vulnerability affects Cisco Aggregation Services Router (ASR) 9000 Series when the following conditions are met:
For information about which Cisco IOS XR Software releases are vulnerable, see the Fixed Software section of this advisory.
Determining Whether MPLS OAM Is Configured
Administrators can use the show running-config mpls oam command to determine whether MPLS OAM is enabled. The following example shows the output of the command for a device that has the MPLS OAM feature enabled:
RP/0/RSP0/CPU0:ASR9001#show running-config mpls oam
Tue Feb 19 12:45:37.011 UTC
mpls oam
An empty output of this command indicates that the device is not affected by the vulnerability described in this advisory.
Determining the Cisco IOS XR Software Release
To determine which Cisco IOS XR Software release is running on a device and the name of the device on which it is running, administrators can log in to the device and use the show version command in the CLI. If the device is running Cisco IOS XR Software, Cisco IOS XR Software or similar text appears in the system banner. The location and name of the system image file that is currently running on the device appears next to the System image file is text. The name of the hardware product appears on the line after the name of the system image file.
The following example shows the output of the show version command on a device that is running Cisco IOS XR Software release 5.3.3 Service Pack 10:
RP/0/RSP0/CPU0:ASR9001#show version Wed Jan 24 01:32:32.751 EST Cisco IOS XR Software, Version 5.3.3[Default] Copyright (c) 2017 by Cisco Systems, Inc. ROM: System Bootstrap, Version 2.04(20140227:092320) [ASR9K ROMMON], ASR9001 uptime is 6 hours, 17 minutes System image file is "bootflash:disk0/asr9k-os-mbi-5.3.3.sp10-1.0.0/0x100000/mbiasr9k-rp.vm" cisco ASR9K Series (P4040) processor with 8388608K bytes of memory. P4040 processor at 1500MHz, Revision 2.0 ASR-9001 Chassis 2 Management Ethernet 8 TenGigE 20 GigabitEthernet 8 DWDM controller(s) 8 WANPHY controller(s) 44 GigabitEthernet/IEEE 802.3 interface(s) 219k bytes of non-volatile configuration memory. 2880M bytes of hard disk. 3932144k bytes of disk0: (Sector size 512 bytes). Configuration register on node 0/RSP0/CPU0 is 0x2102
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
Cisco has determined that this vulnerability does not affect Cisco Aggregation Services Router (ASR) 9000 Series that are not running Cisco IOS XR Software Release 5.3.3 Service Pack 10 or that have not enabled the MPLS OAM feature. Note: The MPLS OAM feature is not enabled by default on Cisco XR Software.
No other devices running Cisco IOS XR Software are affected. Cisco has also confirmed that this vulnerability does not affect devices running Cisco IOS Software, Cisco IOS XE Software, or Cisco NX-OS Software.
The MPLS OAM feature helps service providers monitor label-switched paths (LSPs) and quickly isolate MPLS forwarding problems to assist with fault detection and troubleshooting in an MPLS network. The vulnerability is due to the incorrect handling of certain MPLS OAM packets. An attacker could exploit this vulnerability by sending malicious MPLS OAM packets to an affected device. To exploit this vulnerability, an attacker must have access to the same MPLS domain as the targeted device, which must be configured to process MPLS OAM packets. An exploitation of this vulnerability could cause the lspv_server process to crash, which could result in a DoS condition requiring manual intervention to recover.
Exploitation of this vulnerability could cause the affected device to generate an error message similar to the following:
#RP/0/RSP0/CPU0:May 14 01:44:57.911 : dumper[60]: %OS-DUMPER-7 DUMP_REQUEST : Dump request for process pkg/bin/lspv_server RP/0/RSP0/CPU0:May 14 01:44:57.913 : dumper[60]: %OS-DUMPER-7-DUMP_ATTRIBUTE : Dump request with attribute 7 for process pkg/bin/lspv_server RP/0/RSP0/CPU0:May 14 01:44:57.913 : dumper[60]: %OS-DUMPER-4-CRASH_INFO : Crashed pid = 561506 (pkg/bin/lspv_server)
Customers are advised to contact their support organization to review the error message and determine whether the device has been affected by exploitation of this vulnerability.
There are no workarounds that address this vulnerability.
Disabling the MPLS OAM feature eliminates the exploit vector. Administrators can disable the MPLS OAM feature by using the no mpls oam command in global configuration mode. This action may be a suitable mitigation until devices that are affected by this vulnerability can be upgraded.
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:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.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 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.
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:
https://www.cisco.com/c/en/us/support/web/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
Cisco has released a software maintenance upgrade (SMU) for Cisco Aggregation Services Router (ASR) 9000 Series that addresses this vulnerability. The fix has also been incorporated into Service Pack 11 for Cisco IOS XR Software Release 5.3.3.
| IOS XR Release |
SMU ID | ASR 9000 SMU Name |
| 5.3.3 | AA14582 | asr9k-px-5.3.3.CSCvk63685 |
The SMU/service pack can be downloaded from the Software Center on Cisco.com.
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 the 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 | 2019-May-15 |
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