Linux Distros Unpatched Vulnerability : CVE-2026-23554

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(302811);
  script_version("1.6");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/05/22");

  script_cve_id("CVE-2026-23554");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-23554");

  script_set_attribute(attribute:"synopsis", value:
"The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be
patched.");
  script_set_attribute(attribute:"description", value:
"The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied
patch available.

  - The Intel EPT paging code uses an optimization to defer flushing of any cached EPT state until the p2m
    lock is dropped, so that multiple modifications done under the same locked region only issue a single
    flush. Freeing of paging structures however is not deferred until the flushing is done, and can result in
    freed pages transiently being present in cached state. Such stale entries can point to memory ranges not
    owned by the guest, thus allowing access to unintended memory regions. (CVE-2026-23554)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/CVE-2026-23554");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2026-23554");
  script_set_attribute(attribute:"solution", value:
"There is no known solution at this time.");
  script_set_attribute(attribute:"agent", value:"unix");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:P/I:P/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-23554");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
  script_set_attribute(attribute:"vendor_unpatched", value:"true");

  script_set_attribute(attribute:"plugin_publication_date", value:"2026/03/17");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:20.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:22.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:24.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:25.10");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:13.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:14.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:xen");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:xen");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Misc.");

  script_copyright(english:"This script is Copyright (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info2.nasl", "set_linux_os_id.nasl");
  script_require_keys("Host/cpu", "Host/local_checks_enabled", "global_settings/vendor_unpatched", "Host/OS/identifier");
  script_require_ports("Host/OS/Debian Linux-12", "Host/OS/Debian Linux-13", "Host/OS/Debian Linux-14", "Host/OS/Ubuntu Linux-16.04", "Host/OS/Ubuntu Linux-18.04", "Host/OS/Ubuntu Linux-20.04", "Host/OS/Ubuntu Linux-22.04", "Host/OS/Ubuntu Linux-24.04", "Host/OS/Ubuntu Linux-25.10");

  exit(0);
}

if (!get_kb_item("global_settings/vendor_unpatched")) exit(0, "Unpatched Vulnerabilities Detection not active.");
if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (empty_or_null(get_one_kb_item("Host/Debian/dpkg-l"))) audit(AUDIT_PACKAGE_LIST_MISSING);

include('linux_unpatched.inc');

var distro_constraints_array = {
  "Debian Linux-12": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "12",
        "pkgs": [
          {"reference": "libxen-dev"},
          {"reference": "libxencall1"},
          {"reference": "libxendevicemodel1"},
          {"reference": "libxenevtchn1"},
          {"reference": "libxenforeignmemory1"},
          {"reference": "libxengnttab1"},
          {"reference": "libxenhypfs1"},
          {"reference": "libxenmisc4.17"},
          {"reference": "libxenstore4"},
          {"reference": "libxentoolcore1"},
          {"reference": "libxentoollog1"},
          {"reference": "xen-doc"},
          {"reference": "xen-hypervisor-4.17-amd64"},
          {"reference": "xen-hypervisor-4.17-amd64-dbg"},
          {"reference": "xen-hypervisor-4.17-arm64"},
          {"reference": "xen-hypervisor-4.17-arm64-dbg"},
          {"reference": "xen-hypervisor-4.17-armhf"},
          {"reference": "xen-hypervisor-4.17-armhf-dbg"},
          {"reference": "xen-hypervisor-common"},
          {"reference": "xen-system-amd64"},
          {"reference": "xen-system-arm64"},
          {"reference": "xen-system-armhf"},
          {"reference": "xen-utils-4.17"},
          {"reference": "xen-utils-4.17-dbg"},
          {"reference": "xen-utils-common"},
          {"reference": "xenstore-utils"}
        ]
      }
    ]
  },
  "Debian Linux-13": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "13",
        "pkgs": [
          {"reference": "libxen-dev"},
          {"reference": "libxencall1"},
          {"reference": "libxendevicemodel1"},
          {"reference": "libxenevtchn1"},
          {"reference": "libxenforeignmemory1"},
          {"reference": "libxengnttab1"},
          {"reference": "libxenhypfs1"},
          {"reference": "libxenmisc4.20"},
          {"reference": "libxenstore4"},
          {"reference": "libxentoolcore1"},
          {"reference": "libxentoollog1"},
          {"reference": "xen-doc"},
          {"reference": "xen-hypervisor-4.20-amd64"},
          {"reference": "xen-hypervisor-4.20-amd64-dbg"},
          {"reference": "xen-hypervisor-4.20-arm64"},
          {"reference": "xen-hypervisor-4.20-arm64-dbg"},
          {"reference": "xen-hypervisor-common"},
          {"reference": "xen-system-amd64"},
          {"reference": "xen-system-arm64"},
          {"reference": "xen-utils-4.20"},
          {"reference": "xen-utils-4.20-dbg"},
          {"reference": "xen-utils-common"},
          {"reference": "xenstore-utils"}
        ]
      }
    ]
  },
  "Debian Linux-14": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14",
        "pkgs": [
          {"reference": "libxen-dev"},
          {"reference": "libxencall1"},
          {"reference": "libxendevicemodel1"},
          {"reference": "libxenevtchn1"},
          {"reference": "libxenforeignmemory1"},
          {"reference": "libxengnttab1"},
          {"reference": "libxenhypfs1"},
          {"reference": "libxenmisc4.20"},
          {"reference": "libxenstore4"},
          {"reference": "libxentoolcore1"},
          {"reference": "libxentoollog1"},
          {"reference": "xen-doc"},
          {"reference": "xen-hypervisor-4.20-amd64"},
          {"reference": "xen-hypervisor-4.20-amd64-dbg"},
          {"reference": "xen-hypervisor-4.20-arm64"},
          {"reference": "xen-hypervisor-4.20-arm64-dbg"},
          {"reference": "xen-hypervisor-common"},
          {"reference": "xen-system-amd64"},
          {"reference": "xen-system-arm64"},
          {"reference": "xen-utils-4.20"},
          {"reference": "xen-utils-4.20-dbg"},
          {"reference": "xen-utils-common"},
          {"reference": "xenstore-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "libxen-4.6"},
          {"reference": "libxen-dev"},
          {"reference": "libxenstore3.0"},
          {"reference": "xen-hypervisor-4.4-amd64"},
          {"reference": "xen-hypervisor-4.4-arm64"},
          {"reference": "xen-hypervisor-4.4-armhf"},
          {"reference": "xen-hypervisor-4.5-amd64"},
          {"reference": "xen-hypervisor-4.5-arm64"},
          {"reference": "xen-hypervisor-4.5-armhf"},
          {"reference": "xen-hypervisor-4.6-amd64"},
          {"reference": "xen-hypervisor-4.6-arm64"},
          {"reference": "xen-hypervisor-4.6-armhf"},
          {"reference": "xen-system-amd64"},
          {"reference": "xen-system-arm64"},
          {"reference": "xen-system-armhf"},
          {"reference": "xen-utils-4.6"},
          {"reference": "xen-utils-common"},
          {"reference": "xenstore-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "libxen-4.9"},
          {"reference": "libxen-dev"},
          {"reference": "libxenstore3.0"},
          {"reference": "xen-hypervisor-4.6-amd64"},
          {"reference": "xen-hypervisor-4.6-arm64"},
          {"reference": "xen-hypervisor-4.6-armhf"},
          {"reference": "xen-hypervisor-4.7-amd64"},
          {"reference": "xen-hypervisor-4.7-arm64"},
          {"reference": "xen-hypervisor-4.7-armhf"},
          {"reference": "xen-hypervisor-4.8-amd64"},
          {"reference": "xen-hypervisor-4.8-arm64"},
          {"reference": "xen-hypervisor-4.8-armhf"},
          {"reference": "xen-hypervisor-4.9-amd64"},
          {"reference": "xen-hypervisor-4.9-arm64"},
          {"reference": "xen-hypervisor-4.9-armhf"},
          {"reference": "xen-system-amd64"},
          {"reference": "xen-system-arm64"},
          {"reference": "xen-system-armhf"},
          {"reference": "xen-utils-4.9"},
          {"reference": "xen-utils-common"},
          {"reference": "xenstore-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "xen"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "xen"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "xen"}
        ]
      }
    ]
  },
  "Ubuntu Linux-25.10": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "25.10",
        "pkgs": [
          {"reference": "xen"}
        ]
      }
    ]
  }
};

var distro_constraints_values = linux_unpatched::get_distro_constraints(distro_constraints_arr:distro_constraints_array);
if (empty_or_null(distro_constraints_values)) audit(AUDIT_HOST_NOT, 'affected');
var report = linux_unpatched::check_unpatched_constraints(distro_constraints_values:distro_constraints_values);

if (!empty_or_null(report))
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_WARNING,
      extra      : report
  );
  exit(0);
}
else
{
  audit(AUDIT_HOST_NOT, 'affected');
}