{
  "document": {
    "acknowledgments": [
      {
        "summary": "Cisco would like to thank Adam Haleen of Cellcom Wireless for finding and reporting this vulnerability."
      }
    ],
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "notes": [
      {
        "category": "summary",
        "text": "A vulnerability in the Secure Shell (SSH) authentication function of Cisco IOS XR Software could allow an authenticated, remote attacker to successfully log in to an affected device using two distinct usernames.\r\n\r\nThe vulnerability is due to a logic error that may occur when certain sequences of actions are processed during an SSH login event on the affected device. An attacker could exploit this vulnerability by initiating an SSH session to the device with a specific sequence that presents the two usernames. A successful exploit could result in logging data misrepresentation, user enumeration, or, in certain circumstances, a command authorization bypass.\r\n\r\nSee the Details [\"#details\"] section for more information.\r\n\r\nThere 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-20190605-iosxr-ssh [\"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190605-iosxr-ssh\"]",
        "title": "Summary"
      },
      {
        "category": "general",
        "text": "This vulnerability affects Cisco IOS XR Software when the SSH server is enabled.\r\n\r\nFor information about affected software releases, see the Fixed Software [\"#fs\"] section in this advisory.",
        "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": "The impacts of this vulnerability when the SSH server is enabled are as follows:\r\n\r\nSome logged events will be attributed to the impersonated user.\r\n\r\nExample: Authenticated Attacker A who is assigned the operator task group exploits the vulnerability to impersonate Admin B who is assigned the sysadmin task group. In this case, the attacker could execute all commands that are assigned to the operator task group, but the commands would be reported as being issued by Admin B.\r\nUsername and user task group enumeration can be performed.\r\n\r\nExample: Authenticated Attacker A exploits the vulnerability to impersonate Admin B. If Attacker A issues the CLI command show user \u003coptions\u003e, relevant information for Admin B will be returned. If the Admin B username does not exist, the command will not be executed.\r\nAdditionally, if the authentication, authorization, and accounting (AAA) command authorization feature is enabled with the configuration command aaa authorization commands \u003coptions\u003e, AAA command authorization bypass can occur.\r\n\r\nThe vulnerability is due to a logic error that results in the authenticated username being tied to the correct task groups; however, the alternate username is tied to the command authorization requests. The attacker will always retain the task groups that they were assigned as part of the successful authenticated username.\r\n\r\nThe impact of this vulnerability if the command being executed by the authenticated attacker is allowed as part of their task group configuration and AAA command authorization is configured on the device, is as follows:\r\n\r\nThe command will be sent to the AAA server to validate that the command is authorized. This authorization request will be sent as the impersonated username, which may allow the authenticated attacker to execute unauthorized commands.\r\n\r\nExample: Authenticated Attacker A who is assigned the operator task group exploits the vulnerability to impersonate Admin B who is assigned the sysadmin task group. If Attacker A tries to execute a command that is not allowed by the operator task group, but is authorized to the sysadmin group, the command will not be authorized and is not sent to the AAA server for authorization.\r\n\r\n\r\nExample: Authenticated Attacker A who is assigned the operator task group, but with command restrictions imposed via their AAA profile, exploits the vulnerability to impersonate Admin B who is assigned the operator task group, but with no command restrictions imposed via their AAA profile.  If Attacker A tries to execute a command that is allowed by the operator task group, but not allowed in their AAA profile, the command  will be authorized because the command authorization check is performed using the Admin B username.",
        "title": "Details"
      },
      {
        "category": "general",
        "text": "There are no workarounds that address this vulnerability.",
        "title": "Workarounds"
      },
      {
        "category": "general",
        "text": "Cisco will release free software updates [\"https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html#fixes\"] 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 [\"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, 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.\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:  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\nCisco is releasing the following software maintenance upgrades (SMUs) that address this vulnerability:\r\n                                SMU ID               Platform               Release                                                AA15541               ASR9K-PX              6.1.4                                   AA15542               CRS-PX              6.1.4                                  AA15514              ASR9K-PX               6.3.3                                   AA15515              NCS5500               6.3.3                                  AA15516              NCS6K               6.3.3                                  AA15534              NCS6K              6.4.2                                  AA15526              ASR9K-PX\r\n              6.5.2                                  AA15527              ASR9K-X64\r\n              6.5.2                                  AA15528              NCS5500              6.5.2\r\nThis vulnerability is first fixed in Cisco IOS XR Software Releases 6.5.3, 6.6.2, and 7.0.0.",
        "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": "Cisco would like to thank Adam Haleen of Cellcom Wireless for finding and reporting this vulnerability.",
        "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": "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 Secure Shell Authentication Vulnerability",
        "url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190605-iosxr-ssh"
      },
      {
        "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-20190605-iosxr-ssh",
        "url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190605-iosxr-ssh"
      },
      {
        "category": "external",
        "summary": "free software updates",
        "url": "https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html#fixes"
      },
      {
        "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": "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": "https://sec.cloudapps.cisco.com/security/center/resources/security_vulnerability_policy.html"
      }
    ],
    "title": "Cisco IOS XR Software Secure Shell Authentication Vulnerability",
    "tracking": {
      "current_release_date": "2019-06-05T16:00:00+00:00",
      "generator": {
        "date": "2022-09-03T03:08:33+00:00",
        "engine": {
          "name": "TVCE"
        }
      },
      "id": "cisco-sa-20190605-iosxr-ssh",
      "initial_release_date": "2019-06-05T16:00:00+00:00",
      "revision_history": [
        {
          "date": "2019-06-05T13:18:56+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-2019-1842",
      "ids": [
        {
          "system_name": "Cisco Bug ID",
          "text": "CSCvo03672"
        }
      ],
      "notes": [
        {
          "category": "other",
          "text": "Complete.",
          "title": "Affected Product Comprehensiveness"
        }
      ],
      "product_status": {
        "known_affected": [
          "CSAFPID-5834"
        ]
      },
      "release_date": "2019-06-05T16:00:00+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": 5.4,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
            "version": "3.0"
          },
          "products": [
            "CSAFPID-5834"
          ]
        }
      ],
      "title": "Cisco IOS XR Software Secure Shell Privilege Escalation Vulnerability "
    }
  ]
}