Headline
CVE-2020-3118: Cisco Security Advisory: Cisco IOS XR Software Cisco Discovery Protocol Format String Vulnerability
A vulnerability in the Cisco Discovery Protocol implementation for Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to execute arbitrary code or cause a reload on an affected device. The vulnerability is due to improper validation of string input from certain fields in Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to cause a stack overflow, which could allow the attacker to execute arbitrary code with administrative privileges on an affected device. Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).
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.htmlAdditionally, 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.htmlCustomers 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
In the following table, the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability.
Cisco IOS XR Software Release
First Fixed Release for This Vulnerability
Earlier than 6.6
Appropriate SMU
6.61
6.6.3 or appropriate SMU
7.0
7.0.2 (Mar 2020) or appropriate SMU
7.1
Not vulnerable
1. Customers who are running Cisco IOS XR Software Release 6.6 on white box routers are advised to upgrade to Release 6.6.12 and then install the software maintenance upgrade (SMU). Customers who are running Cisco IOS XR Software Release 6.6 on other platforms are advised to upgrade to Release 6.6.3.
The following SMUs are also available for Cisco IOS XR Software:
Cisco IOS XR Software Release
Platform
SMU Name
5.2.5
NCS6K
ncs6k-5.2.5.CSCvr78185
6.4.2
ASR9K-PX
asr9k-px-6.4.2.CSCvr78185
CRS-PX
hfr-px-6.4.2.CSCvr78185
6.5.3
ASR9K-PX
asr9k-px-6.5.3.CSCvr78185
ASR9K-X64
asr9k-x64-6.5.3.CSCvr78185
NCS540
ncs540-6.5.3.CSCvr78185
NCS5K
ncs5k-6.5.3.CSCvr78185
NCS5500
ncs5500-6.5.3.CSCvr78185
XRV9K
xrv9k-6.5.3.CSCvr78185
6.6.12
White box
iosxrwbd-6.6.12.CSCvr78185
6.6.25
NCS560
ncs560-6.6.25.CSCvr78185
7.0.1
NCS540L
ncs540l-7.0.1.CSCvr78185
For details on where to download and how to install SMUs in Cisco IOS XR Software, see the IOS XR Software Maintenance Updates (SMUs) guide.