UBUNTU-CVE-2019-18423 (CVE-2019-18423)

Vulnerability from osv_ubuntu – Published: 2019-10-31 14:15 – Updated: 2026-04-22 07:39 – Source website
VLAI
Details

An issue was discovered in Xen through 4.12.x allowing ARM guest OS users to cause a denial of service via a XENMEM_add_to_physmap hypercall. p2m->max_mapped_gfn is used by the functions p2m_resolve_translation_fault() and p2m_get_entry() to sanity check guest physical frame. The rest of the code in the two functions will assume that there is a valid root table and check that with BUG_ON(). The function p2m_get_root_pointer() will ignore the unused top bits of a guest physical frame. This means that the function p2m_set_entry() will alias the frame. However, p2m->max_mapped_gfn will be updated using the original frame. It would be possible to set p2m->max_mapped_gfn high enough to cover a frame that would lead p2m_get_root_pointer() to return NULL in p2m_get_entry() and p2m_resolve_translation_fault(). Additionally, the sanity check on p2m->max_mapped_gfn is off-by-one allowing "highest mapped + 1" to be considered valid. However, p2m_get_root_pointer() will return NULL. The problem could be triggered with a specially crafted hypercall XENMEM_add_to_physmap{, _batch} followed by an access to an address (via hypercall or direct access) that passes the sanity check but cause p2m_get_root_pointer() to return NULL. A malicious guest administrator may cause a hypervisor crash, resulting in a Denial of Service (DoS). Xen version 4.8 and newer are vulnerable. Only Arm systems are vulnerable. x86 systems are not affected.

Severity
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libxen-4.6",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "libxenstore3.0",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-hypervisor-4.4-amd64",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-hypervisor-4.4-arm64",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-hypervisor-4.4-armhf",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-hypervisor-4.5-amd64",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-hypervisor-4.5-arm64",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-hypervisor-4.5-armhf",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-hypervisor-4.6-amd64",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-hypervisor-4.6-arm64",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-hypervisor-4.6-armhf",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-system-amd64",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-system-arm64",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-system-armhf",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-utils-4.6",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xen-utils-common",
            "binary_version": "4.6.5-0ubuntu1.4"
          },
          {
            "binary_name": "xenstore-utils",
            "binary_version": "4.6.5-0ubuntu1.4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "xen",
        "purl": "pkg:deb/ubuntu/xen@4.6.5-0ubuntu1.4?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.5.1-0ubuntu1",
        "4.5.1-0ubuntu2",
        "4.6.0-1ubuntu1",
        "4.6.0-1ubuntu2",
        "4.6.0-1ubuntu4",
        "4.6.0-1ubuntu4.1",
        "4.6.0-1ubuntu4.2",
        "4.6.0-1ubuntu4.3",
        "4.6.5-0ubuntu1",
        "4.6.5-0ubuntu1.1",
        "4.6.5-0ubuntu1.2",
        "4.6.5-0ubuntu1.4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libxen-4.9",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "libxenstore3.0",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.6-amd64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.6-arm64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.6-armhf",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.7-amd64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.7-arm64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.7-armhf",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.8-amd64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.8-arm64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.8-armhf",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.9-amd64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.9-arm64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-hypervisor-4.9-armhf",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-system-amd64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-system-arm64",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-system-armhf",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-utils-4.9",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xen-utils-common",
            "binary_version": "4.9.2-0ubuntu1"
          },
          {
            "binary_name": "xenstore-utils",
            "binary_version": "4.9.2-0ubuntu1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "xen",
        "purl": "pkg:deb/ubuntu/xen@4.9.2-0ubuntu1?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.9.0-0ubuntu3",
        "4.9.0-0ubuntu4",
        "4.9.2-0ubuntu1"
      ]
    }
  ],
  "aliases": [],
  "details": "An issue was discovered in Xen through 4.12.x allowing ARM guest OS users to cause a denial of service via a XENMEM_add_to_physmap hypercall. p2m-\u003emax_mapped_gfn is used by the functions p2m_resolve_translation_fault() and p2m_get_entry() to sanity check guest physical frame. The rest of the code in the two functions will assume that there is a valid root table and check that with BUG_ON(). The function p2m_get_root_pointer() will ignore the unused top bits of a guest physical frame. This means that the function p2m_set_entry() will alias the frame. However, p2m-\u003emax_mapped_gfn will be updated using the original frame. It would be possible to set p2m-\u003emax_mapped_gfn high enough to cover a frame that would lead p2m_get_root_pointer() to return NULL in p2m_get_entry() and p2m_resolve_translation_fault(). Additionally, the sanity check on p2m-\u003emax_mapped_gfn is off-by-one allowing \"highest mapped + 1\" to be considered valid. However, p2m_get_root_pointer() will return NULL. The problem could be triggered with a specially crafted hypercall XENMEM_add_to_physmap{, _batch} followed by an access to an address (via hypercall or direct access) that passes the sanity check but cause p2m_get_root_pointer() to return NULL. A malicious guest administrator may cause a hypervisor crash, resulting in a Denial of Service (DoS). Xen version 4.8 and newer are vulnerable. Only Arm systems are vulnerable. x86 systems are not affected.",
  "id": "UBUNTU-CVE-2019-18423",
  "modified": "2026-04-22T07:39:07Z",
  "published": "2019-10-31T14:15:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2019-18423"
    },
    {
      "type": "REPORT",
      "url": "https://xenbits.xen.org/xsa/advisory-301.html"
    },
    {
      "type": "REPORT",
      "url": "http://www.openwall.com/lists/oss-security/2019/10/31/4"
    },
    {
      "type": "REPORT",
      "url": "http://xenbits.xen.org/xsa/advisory-301.html"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2019-18423"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2019-18423"
  ]
}



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