Linux Distros Unpatched Vulnerability : CVE-2026-80893

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

include('compat.inc');

if (description)
{
  script_id(343021);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/04");

  script_cve_id("CVE-2026-80893");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-80893");

  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.

  - mm/hugetlb: fix swap entry corruption when clearing uffd-wp at fork() copy_hugetlb_page_range() clears the
    uffd-wp bit of migration and hwpoison entries with huge_pte_clear_uffd_wp(), which operates on the
    present-PTE bit position. Swap entries keep the uffd-wp state elsewhere -- the migration branch reads and
    sets it with pte_swp_uffd_wp() and pte_swp_mkuffd_wp() -- and the present-PTE position falls into the swap
    payload. On x86-64 it lands in the inverted swap offset, where a naturally-aligned hugetlb PFN always has
    the affected bit set, so the clear advances the encoded PFN by two pages. No userfaultfd needs to be
    involved: the clear is guarded only by the child VMA not being uffd-wp registered, so a plain fork() with
    an in-flight hugetlb migration entry (or a poisoned hugetlb page) corrupts the entry copied into the
    child. Instrumenting the clear and forking after MADV_HWPOISON on a 2MB anon hugetlb page shows: offset
    before=120e00 offset after =120e02 The fallout is mostly latent: rmap walks match migration entries by
    folio range and remove_migration_pte() rebuilds the PTE from the folio, so a within-folio PFN skew heals
    once migration completes. But any path that re-encodes the corrupted offset -- e.g.
    hugetlb_change_protection() rewriting a writable migration entry via
    make_readable_migration_entry(swp_offset(entry)) -- propagates it. Migration entries legitimately carry
    uffd-wp, so clear it with pte_swp_clear_uffd_wp(), matching copy_nonpresent_pte() and move_huge_pte(). A
    hwpoison entry, on the other hand, never carries the uffd-wp bit: it is installed fresh by
    make_hwpoison_entry() (try_to_unmap_one() does not preserve uffd-wp on the hwpoison path) and
    hugetlb_change_protection() leaves hwpoison entries untouched. There was nothing to clear there, only the
    corruption, so drop the clear entirely. (CVE-2026-80893)

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-2026-80893");
  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:N/AC:L/Au:N/C:P/I:P/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/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-2026-80893");

  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:"vuln_publication_date", value:"2026/09/04");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/04");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:linux");
  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");

  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": "btrfs-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "cdrom-core-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "ext4-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "fat-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "isofs-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "jfs-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "kernel-image-6.1.0-50-alpha-generic-di"},
          {"reference": "linux-doc"},
          {"reference": "linux-doc-6.1"},
          {"reference": "linux-headers-6.1.0"},
          {"reference": "linux-source"},
          {"reference": "linux-source-6.1"},
          {"reference": "linux-support-6.1.0"},
          {"reference": "loop-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "nic-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "nic-shared-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "nic-wireless-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "pata-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "ppp-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "scsi-core-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "scsi-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "scsi-nic-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "serial-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "usb-serial-modules-6.1.0-50-alpha-generic-di"},
          {"reference": "xfs-modules-6.1.0-50-alpha-generic-di"}
        ]
      }
    ]
  }
};

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 third_party_support = get_kb_item('Host/OS/extended-third-party');
if (!empty_or_null(third_party_support)) {
    var third_party_vendors = distro_constraints_values['third_party'];
    if (!empty_or_null(third_party_vendors)) {
        var vendor;
        foreach vendor (third_party_vendors) {
            if (vendor == third_party_support) exit(0, 'A third party management patch is available for this vulnerability from ' + vendor + '.\n');
        }
    }
}

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');
}