Headline
CVE-2019-1910: Cisco Security Advisory: Cisco IOS XR Software Intermediate System-to-Intermediate System Denial of Service Vulnerability
A vulnerability in the implementation of the Intermediate System–to–Intermediate System (IS–IS) routing protocol functionality in Cisco IOS XR Software could allow an unauthenticated attacker who is in the same IS–IS area to cause a denial of service (DoS) condition. The vulnerability is due to incorrect processing of crafted IS–IS link-state protocol data units (PDUs). An attacker could exploit this vulnerability by sending a crafted link-state PDU to an affected system to be processed. A successful exploit could allow the attacker to cause all routers within the IS–IS area to unexpectedly restart the IS–IS process, resulting in a DoS condition. This vulnerability affects Cisco devices if they are running a vulnerable release of Cisco IOS XR Software earlier than Release 6.6.3 and are configured with the IS–IS routing protocol. Cisco has confirmed that this vulnerability affects both Cisco IOS XR 32-bit Software and Cisco IOS XR 64-bit Software.
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
At time of publication, Cisco had fixed this vulnerability in Cisco IOS XR Software Releases 6.6.25 and 6.6.3.
At time of publication, the SMUs in the following table were available. This table will be updated if any new SMUs are released. Customers who require SMUs for other platforms and releases are advised to contact their support organization.
IOS XR Release
SMU ID
Platform
SMU Name
6.5.3
AA15778
ASR9000
asr9k-px-6.5.3.CSCvq451181
6.6.1
AA15881
NC56K
ncs6k-6.6.1.CSCvq45118.tar1
1The SMUs contain the fixes for the vulnerabilities described in cisco-sa-20190807-iosxr-isis-dos-1910 and cisco-sa-20190807-iosxr-isis-dos-1918 advisories.
Customers can download the SMUs from the Software Center on Cisco.com by doing the following:
- Click Browse All.
- Choose IOS and NX-OS Software > IOS XR > IOS XR Software > Optical Networking or Routers.
- Choose the appropriate product and model.
- Access releases by using the left pane of the appropriate product page.