{
  "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 handling of specific Ethernet frames by Cisco IOS XR Software for various Cisco Network Convergence System (NCS) platforms could allow an unauthenticated, adjacent attacker to cause critical priority packets to be dropped, resulting in a denial of service (DoS) condition.\r\n\r\nThis vulnerability is due to incorrect classification of certain types of Ethernet frames that are received on an interface. An attacker could exploit this vulnerability by sending specific types of Ethernet frames to or through the affected device. A successful exploit could allow the attacker to cause control plane protocol relationships to fail, resulting in a DoS condition. For more information, see the Details [\"#details\"] section of this advisory.\r\n\r\nCisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.\r\n\r\n\r\n\r\nThis advisory is part of the September 2024 release of the Cisco IOS XR Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2024 Semiannual Cisco IOS XR Software Security Advisory Bundled Publication [\"https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-75416\"].",
        "title": "Summary"
      },
      {
        "category": "general",
        "text": "This vulnerability affects the following Cisco NCS devices if they are running a vulnerable release of Cisco IOS XR Software and if they are configured with Layer 2 Ethernet services:\r\n\r\nNCS 55A1 Fixed Chassis\r\nNCS 55A2 Fixed Chassis\r\nNCS 540 Series Routers (except N540-24Q8L2DD-SYS)\r\nNCS 560 Series Routers\r\nNCS 5500 Series Modular Chassis1\r\nNCS 5501 Fixed Chassis\r\nNCS 5502 Fixed Chassis\r\n\r\n1. All product IDs except those starting with NCS57 are affected by this vulnerability. For more information, see the Cisco Network Convergence System 5500 Series Modular Chassis [\"https://www.cisco.com/c/en/us/products/collateral/routers/network-convergence-system-5500-series/datasheet-c78-736270.html\"] data sheet.\r\n\r\nFor information about which Cisco software releases are vulnerable, see the Fixed Software [\"#fs\"] section of this advisory.\r\n\r\nDetermine Whether the Device is Configured with Layer 2 Ethernet Services\r\n\r\nTo determine whether Layer 2 services are configured on the device, use the command show running-config | include l2transport. If output is returned, the device is affected, as shown in the following example:\r\n\r\n\r\nRP/0/RP0/CPU0:NCS5501#show running-config | include l2transport\r\nTue Jan 16 01:14:07.977 UTC\r\nBuilding configuration...\r\ninterface GigabitEthernet0/0/0/1.200 l2transport\r\nRP/0/RP0/CPU0:NCS5501#\r\n\r\nIf the output returns no information, the device is not affected by this vulnerability.",
        "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.\r\n\r\nCisco has confirmed that this vulnerability does not affect the following Cisco products:\r\n\r\nIOS Software\r\nIOS XE Software\r\nIOS XR Platforms that are not listed in the Vulnerable Products [\"#vp\"] section of this advisory\r\nNX-OS Software",
        "title": "Products Confirmed Not Vulnerable"
      },
      {
        "category": "general",
        "text": "When specific frames are received on the Layer 2 interface, they are incorrectly classified as traffic class 7 virtual output queue (TC7 VOQ). If enough of these frames are sent at sustained rates, the VOQ will start to drop packets in TC7. The affected port is the interface by which the Layer 2 traffic receives egresses from the device. In most cases, this is the core interface of a service provider.\r\n\r\nBecause control plane traffic is also handled within this queue, this vulnerability could cause keepalive or hello packets to be dropped, resulting in a DoS condition for protocols such as OSPF, Intermediate System-to-Intermediate System (ISIS), Bidirectional Forwarding Detection (BFD), Border Gateway Protocol (BGP), and Label Distribution Protocol (LDP).\r\n\r\nTo monitor the state of the VOQs, use the show controllers npu stats voq ingress interface command. The following example shows command output of a TC_7 VOQ that is being exhausted:\r\n\r\n\r\nRP/0/RP0/CPU0:NCS-5501#show controllers npu stats voq ingress interface tenGigE 0/0/0/2 instance 0 location 0/0/CPU0\r\nWed Mar 13 16:00:00.000 UTC\r\nInterface Name    =    Te0/0/0/2\r\nInterface Handle  =          118\r\nLocation          =     0/0/CPU0\r\nAsic Instance     =            0\r\nVOQ Base          =         1088\r\nPort Speed(kbps)  =     10000000\r\nLocal Port        =        local\r\n       ReceivedPkts    ReceivedBytes   DroppedPkts     DroppedBytes\r\n-------------------------------------------------------------------\r\nCore-0:\r\nTC_0 = 0               0               0               0\r\nTC_1 = 47708616        37410160369     0               0\r\nTC_2 = 0               0               0               0\r\nTC_3 = 0               0               0               0\r\nTC_4 = 0               0               0               0\r\nTC_5 = 0               0               0               0\r\nTC_6 = 0               0               0               0\r\nTC_7 = 11033161168     1108832775990   6905125762      791656829609\r\nCore-1:\r\nTC_0 = 0               0               0               0\r\nTC_1 = 0               0               0               0\r\nTC_2 = 0               0               0               0\r\nRP/0/RP0/CPU0:NCS-5501#",
        "title": "Details"
      },
      {
        "category": "general",
        "text": "There are no workarounds that address this vulnerability.",
        "title": "Workarounds"
      },
      {
        "category": "general",
        "text": "Cisco has released free software updates [\"https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html#ssu\"] that address the vulnerability described in this advisory. Customers with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels.\r\n\r\nCustomers 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\nThe Cisco Support and Downloads page [\"https://www.cisco.com/c/en/us/support/index.html\"] on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool.\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 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  Customers Without Service Contracts\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: https://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\nIn the following table, the left column lists Cisco software releases or trains. The right column indicates whether a release (train) is affected by the vulnerability that is described in this advisory and the first release that includes the fix for this vulnerability.\r\n        Cisco IOS XR Software Release  First Fixed Release          7.6 and earlier  Not affected.      7.7  Migrate to a fixed release.      7.8  Migrate to a fixed release.      7.9  Migrate to a fixed release.      7.10  7.10.2      7.11  7.11.1      24.1  24.1.1\r\nCisco has released the following SMUs to address this vulnerability. Customers who require SMUs for releases that are not listed in the following table are advised to contact their support organization.\r\n        Cisco IOS XR Software Release  Platform  SMU Name          7.8.2  NCS540  ncs540-7.8.2.CSCwh30122      7.9.2  IOSXRWBD\r\nNCS5500  iosxrwbd-7.9.2.CSCwh30122\r\nncs5500-7.9.2.CSCwh30122\r\nThe Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.",
        "title": "Fixed Software"
      },
      {
        "category": "general",
        "text": "To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy [\"http://www.cisco.com/web/about/security/psirt/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 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.\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": "psirt@cisco.com",
      "issuing_authority": "Cisco PSIRT",
      "name": "Cisco",
      "namespace": "https://wwww.cisco.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "Cisco IOS XR Software Network Convergence System Denial of Service Vulnerability",
        "url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-l2services-2mvHdNuC"
      },
      {
        "category": "external",
        "summary": "Cisco Event Response: September 2024 Semiannual Cisco IOS XR Software Security Advisory Bundled Publication",
        "url": "https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-75416"
      },
      {
        "category": "external",
        "summary": "Cisco Security Vulnerability Policy",
        "url": "https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html"
      },
      {
        "category": "external",
        "summary": "Cisco Network Convergence System 5500 Series Modular Chassis",
        "url": "https://www.cisco.com/c/en/us/products/collateral/routers/network-convergence-system-5500-series/datasheet-c78-736270.html"
      },
      {
        "category": "external",
        "summary": "free software updates",
        "url": "https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html#ssu"
      },
      {
        "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": "Cisco Support and Downloads page",
        "url": "https://www.cisco.com/c/en/us/support/index.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 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": "Security Vulnerability Policy",
        "url": "http://www.cisco.com/web/about/security/psirt/security_vulnerability_policy.html"
      }
    ],
    "title": "Cisco IOS XR Software Network Convergence System Denial of Service Vulnerability",
    "tracking": {
      "current_release_date": "2024-09-11T16:00:00+00:00",
      "generator": {
        "date": "2024-09-11T15:46:57+00:00",
        "engine": {
          "name": "TVCE"
        }
      },
      "id": "cisco-sa-l2services-2mvHdNuC",
      "initial_release_date": "2024-09-11T16:00:00+00:00",
      "revision_history": [
        {
          "date": "2024-09-11T15:46:30+00:00",
          "number": "1.0.0",
          "summary": "Initial public release."
        }
      ],
      "status": "final",
      "version": "1.0.0"
    }
  },
  "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-2024-20317",
      "ids": [
        {
          "system_name": "Cisco Bug ID",
          "text": "CSCwh30122"
        }
      ],
      "notes": [
        {
          "category": "other",
          "text": "Complete.",
          "title": "Affected Product Comprehensiveness"
        }
      ],
      "product_status": {
        "known_affected": [
          "CSAFPID-5834"
        ]
      },
      "release_date": "2024-09-11T16:00:00+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:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H",
            "version": "3.1"
          },
          "products": [
            "CSAFPID-5834"
          ]
        }
      ],
      "title": "Cisco IOS XR Software Layer 2 Services Denial of Service Vulnerability"
    }
  ]
}