{
  "document": {
    "acknowledgments": [
      {
        "summary": "This vulnerability was found during the resolution of a Cisco TAC support case."
      }
    ],
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "notes": [
      {
        "category": "summary",
        "text": "A vulnerability in the implementation of Intermediate System\u2013to\u2013Intermediate System (IS\u2013IS) 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.\r\n\r\nThe vulnerability is due to incorrect processing of IS\u2013IS link-state protocol data units (PDUs). An attacker could exploit this vulnerability by sending specific link-state PDUs to an affected system to be processed. A successful exploit could allow the attacker to cause incorrect calculations used in the weighted remote shared risk link groups (SRLG) or in the IGP Flexible Algorithm. It could also cause tracebacks to the logs or potentially cause the receiving device to crash the IS\u2013IS process, resulting in a DoS condition.\r\n\r\nCisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.\r\n\r\nThis advisory is available at the following link:\r\nhttps://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-iosxr-isis-dos-1918 [\"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-iosxr-isis-dos-1918\"]\r\n\r\nA companion advisory is available at the following link:\r\nhttps://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-iosxr-isis-dos-1910 [\"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-iosxr-isis1-dos\"]",
        "title": "Summary"
      },
      {
        "category": "general",
        "text": "This vulnerability affects Cisco devices if they are running Cisco IOS XR Software releases later than 6.5.1 and earlier than 6.6.3.\r\n\r\nCisco has confirmed that this vulnerability affects both Cisco IOS XR 32-bit Software and Cisco IOS XR 64-bit Software.\r\n\r\n\r\n  Determining Whether the Device Has a Vulnerable Configuration\r\n  To determine if the device is configured for IS\u2013IS routing, administrators can use the show running-config router isis EXEC command in the CLI. If the router is configured with IS\u2013IS routing, it will return output. The following example shows the output of the show running-config router isis command on a device that is configured as a level 1 IS\u2013IS router.\r\n\r\nThe device is affected if it is configured as one of the following: is-type level-1, level-1-2 or level-2-only.\r\n\r\n\r\nRP/0/RSP1/CPU0:IOSXR#show running-config router isis\r\nSun May 26 05:20:23.088 UTC  router isis core  is-type level-1  net 49.0001.1921.6825.5091.00  address-family ipv4 unicast  !  interface TenGigE0/0/0/1    address-family ipv4 unicast   !\r\n    For the device to be exploitable, it would need at least one formed IS\u2013IS adjacency.\r\n\r\nRP/0/RSP1/CPU0:IOSXR#show isis adjacency\r\n  IS-IS p Level-1 adjacencies:  System Id      Interface        SNPA           State Hold     Changed  NSF      BFD  12a4           PO0/1/0/1        *PtoP*         Up    23       00:00:06 Capable  Init  12a4           TenGigE0/0/0/1   0004.2893.f2f6 Up    56       00:04:01 Capable  Up    Total adjacency count: 2   !",
        "title": "Vulnerable Products"
      },
      {
        "category": "general",
        "text": "Only products listed in the Vulnerable Products [\"#vp\"] section of this advisory are known to be affected by this vulnerability.",
        "title": "Products Confirmed Not Vulnerable"
      },
      {
        "category": "general",
        "text": "Cisco recommends that customers ensure the authentication of routers within the IS\u2013IS area for adjacency establishment (Hello packets) and for link-state PDUs when implementing IS\u2013IS. If this best practice is followed, then only an authenticated adjacency within the same IS-IS area that sends the specific IS\u2013IS link-state PDU could exploit this vulnerability.\r\n\r\nCisco also recommends that customers enable Non-Stop Forwarding and/or Non-Stop Routing.",
        "title": "Details"
      },
      {
        "category": "general",
        "text": "There are no workarounds that address this vulnerability. However, following Cisco best practices and ensuring that IS\u2013IS authentication is enabled for adjacencies (Hello packets) and link-state PDUs would restrict this vulnerability to only authenticated link-state PDUs. For example:\r\n\r\n\r\nrouter isis core\r\nlsp-password hmac-md5 encrypted 13061E010803  interface TenGigE0/0/0/6    hello-password hmac-md5 encrypted 094F471A1A0A  !\r\n\r\n\r\n\r\nFor more information on IS\u2013IS Authentication, see the IS\u2013IS Authentication chapter [\"https://www.cisco.com/c/en/us/td/docs/routers/xr12000/software/xr12k_r4-0/routing/configuration/guide/rc40xr12k_chapter3.html#con_1276647\"] of Implementing IS\u2013IS on Cisco IOS XR Software.",
        "title": "Workarounds"
      },
      {
        "category": "general",
        "text": "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:\r\nhttps://www.cisco.com/c/en/us/products/end-user-license-agreement.html [\"https://www.cisco.com/c/en/us/products/end-user-license-agreement.html\"]\r\n\r\nAdditionally, 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.\r\n\r\nWhen considering software upgrades [\"https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html#fixes\"], customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page [\"https://www.cisco.com/go/psirt\"], to determine exposure and a complete upgrade solution.\r\n\r\nIn 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.\r\n\r\nCustomers Without Service Contracts\r\n\r\nCustomers 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:\r\nhttps://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html [\"https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html\"]\r\n\r\nCustomers 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.\r\n  Fixed Releases\r\n At time of publication, Cisco had fixed this vulnerability in Cisco IOS XR Software Release 6.6.3.\r\n\r\nAt 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.\r\n                                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\r\n1The 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.\r\n\r\nCustomers can download the SMUs from the Software Center [\"https://software.cisco.com/download/home\"] on Cisco.com by doing the following:\r\n\r\nClick Browse All.\r\nChoose IOS and NX-OS Software \u003e IOS XR \u003e IOS XR Software \u003e Optical Networking or Routers.\r\nChoose the appropriate product and model.\r\nAccess releases by using the left pane of the appropriate product page.",
        "title": "Fixed Software"
      },
      {
        "category": "general",
        "text": "To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy [\"https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html\"]. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.",
        "title": "Vulnerability Policy"
      },
      {
        "category": "general",
        "text": "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.",
        "title": "Exploitation and Public Announcements"
      },
      {
        "category": "general",
        "text": "This vulnerability was found during the resolution of a Cisco TAC support case.",
        "title": "Source"
      },
      {
        "category": "legal_disclaimer",
        "text": "THIS DOCUMENT IS PROVIDED ON AN \"AS IS\" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME. CISCO EXPECTS TO UPDATE THIS DOCUMENT AS NEW INFORMATION BECOMES AVAILABLE.\r\n\r\nA standalone copy or paraphrase of the text of this document that omits the distribution URL is an uncontrolled copy and may lack important information or contain factual errors. The information in this document is intended for end users of Cisco products.",
        "title": "Legal Disclaimer"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "Emergency Support:\r\n+1 877 228 7302 (toll-free within North America)\r\n+1 408 525 6532 (International direct-dial)\r\nNon-emergency Support:\r\nEmail: psirt@cisco.com\r\nSupport requests that are received via e-mail are typically acknowledged within 48 hours.",
      "issuing_authority": "Cisco product security incident response is the responsibility of the Cisco Product Security Incident Response Team (PSIRT). The Cisco PSIRT is a dedicated, global team that manages the receipt, investigation, and public reporting of security vulnerability information that is related to Cisco products and networks. The on-call Cisco PSIRT works 24x7 with Cisco customers, independent security researchers, consultants, industry organizations, and other vendors to identify possible security issues with Cisco products and networks.\r\nMore information can be found in Cisco Security Vulnerability Policy available at https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html",
      "name": "Cisco",
      "namespace": "https://wwww.cisco.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "Cisco IOS XR Software Intermediate System-to-Intermediate System Denial of Service Vulnerability",
        "url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-iosxr-isis-dos-1918"
      },
      {
        "category": "external",
        "summary": "Cisco Security Vulnerability Policy",
        "url": "https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html"
      },
      {
        "category": "external",
        "summary": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-iosxr-isis-dos-1918",
        "url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-iosxr-isis-dos-1918"
      },
      {
        "category": "external",
        "summary": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-iosxr-isis-dos-1910",
        "url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190807-iosxr-isis1-dos"
      },
      {
        "category": "external",
        "summary": "IS\u0026ndash;IS Authentication chapter",
        "url": "https://www.cisco.com/c/en/us/td/docs/routers/xr12000/software/xr12k_r4-0/routing/configuration/guide/rc40xr12k_chapter3.html#con_1276647"
      },
      {
        "category": "external",
        "summary": "https://www.cisco.com/c/en/us/products/end-user-license-agreement.html",
        "url": "https://www.cisco.com/c/en/us/products/end-user-license-agreement.html"
      },
      {
        "category": "external",
        "summary": "considering software upgrades",
        "url": "https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html#fixes"
      },
      {
        "category": "external",
        "summary": "Cisco Security Advisories and Alerts page",
        "url": "https://www.cisco.com/go/psirt"
      },
      {
        "category": "external",
        "summary": "https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html",
        "url": "https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html"
      },
      {
        "category": "external",
        "summary": "Software Center",
        "url": "https://software.cisco.com/download/home"
      },
      {
        "category": "external",
        "summary": "Security Vulnerability Policy",
        "url": "https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html"
      }
    ],
    "title": "Cisco IOS XR Software Intermediate System-to-Intermediate System Denial of Service Vulnerability",
    "tracking": {
      "current_release_date": "2019-08-20T15:38:21+00:00",
      "generator": {
        "date": "2022-09-03T03:41:12+00:00",
        "engine": {
          "name": "TVCE"
        }
      },
      "id": "cisco-sa-20190807-iosxr-isis-dos-1918",
      "initial_release_date": "2019-08-07T16:00:00+00:00",
      "revision_history": [
        {
          "date": "2019-08-07T15:45:46+00:00",
          "number": "1.0.0",
          "summary": "Initial public release."
        },
        {
          "date": "2019-08-20T15:38:21+00:00",
          "number": "1.1.0",
          "summary": "Added details about available SMUs."
        }
      ],
      "status": "interim",
      "version": "1.1.0"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "category": "product_family",
            "name": "Cisco IOS XR Software",
            "product": {
              "name": "Cisco IOS XR Software ",
              "product_id": "CSAFPID-5834"
            }
          }
        ],
        "category": "vendor",
        "name": "Cisco"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2019-1918",
      "ids": [
        {
          "system_name": "Cisco Bug ID",
          "text": "CSCvp90854"
        }
      ],
      "notes": [
        {
          "category": "other",
          "text": "Complete.",
          "title": "Affected Product Comprehensiveness"
        }
      ],
      "product_status": {
        "known_affected": [
          "CSAFPID-5834"
        ]
      },
      "release_date": "2019-08-07T16:00:00+00:00",
      "remediations": [
        {
          "category": "vendor_fix",
          "details": "Cisco has released software updates that address this vulnerability.",
          "product_ids": [
            "CSAFPID-5834"
          ],
          "url": "https://software.cisco.com"
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "baseScore": 7.4,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H",
            "version": "3.0"
          },
          "products": [
            "CSAFPID-5834"
          ]
        }
      ],
      "title": "Cisco IOS XR Software Intermediate System to Intermediate System Denial of Service Vulnerability"
    }
  ]
}