Linux Distros Unpatched Vulnerability : CVE-2026-76781

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

include('compat.inc');

if (description)
{
  script_id(346955);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/18");

  script_cve_id("CVE-2026-76781");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-76781");

  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.

  - A flaw was found in libxml2. A local user or an attacker providing a specially crafted XML catalog can
    trigger a NULL pointer dereference during XML catalog parsing. This occurs when a `nextCatalog` element
    lacks its mandatory `catalog` attribute, leading to the application crashing and causing a Denial of
    Service (DoS). (CVE-2026-76781)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://access.redhat.com/security/cve/cve-2026-76781");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2026-76781");
  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:N/I:N/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/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-2026-76781");

  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:"2026/09/17");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/17");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:14.04:-:lts");
  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:26.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:centos:centos:8");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:redhat:enterprise_linux:10");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:redhat:enterprise_linux:8");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:redhat:enterprise_linux:9");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libxml2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:libxml2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:libxml2-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:libxml2-static");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:podman");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:podman-catatonit");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:podman-docker");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:podman-gvproxy");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:podman-manpages");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:podman-plugins");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:podman-remote");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:podman-tests");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:python3-libxml2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:libxml2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:libxml2-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:libxml2-static");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:podman");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:podman-catatonit");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:podman-docker");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:podman-gvproxy");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:podman-manpages");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:podman-plugins");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:podman-remote");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:podman-tests");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:python3-libxml2");
  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/CentOS Linux-8", "Host/OS/Red Hat Enterprise Linux-10", "Host/OS/Red Hat Enterprise Linux-8", "Host/OS/Red Hat Enterprise Linux-9", "Host/OS/Ubuntu Linux-14.04", "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-26.04");

  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/CentOS/rpm-list")) && empty_or_null(get_one_kb_item("Host/Debian/dpkg-l")) && empty_or_null(get_one_kb_item("Host/RedHat/rpm-list"))) audit(AUDIT_PACKAGE_LIST_MISSING);

include('linux_unpatched.inc');

var distro_constraints_array = {
  "Ubuntu Linux-14.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14.04",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-dbg"},
          {"reference": "libxml2-dev"},
          {"reference": "libxml2-doc"},
          {"reference": "libxml2-udeb"},
          {"reference": "libxml2-utils"},
          {"reference": "libxml2-utils-dbg"},
          {"reference": "python-libxml2"},
          {"reference": "python-libxml2-dbg"}
        ]
      }
    ]
  },
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-dbg"},
          {"reference": "libxml2-dev"},
          {"reference": "libxml2-doc"},
          {"reference": "libxml2-utils"},
          {"reference": "libxml2-utils-dbg"},
          {"reference": "python-libxml2"},
          {"reference": "python-libxml2-dbg"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-dbg"},
          {"reference": "libxml2-dev"},
          {"reference": "libxml2-doc"},
          {"reference": "libxml2-udeb"},
          {"reference": "libxml2-utils"},
          {"reference": "python-libxml2"},
          {"reference": "python-libxml2-dbg"},
          {"reference": "python3-libxml2"},
          {"reference": "python3-libxml2-dbg"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-dev"},
          {"reference": "libxml2-doc"},
          {"reference": "libxml2-utils"},
          {"reference": "python-libxml2"},
          {"reference": "python-libxml2-dbg"},
          {"reference": "python3-libxml2"},
          {"reference": "python3-libxml2-dbg"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-dev"},
          {"reference": "libxml2-doc"},
          {"reference": "libxml2-utils"},
          {"reference": "python3-libxml2"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-dev"},
          {"reference": "libxml2-doc"},
          {"reference": "libxml2-utils"},
          {"reference": "python3-libxml2"}
        ]
      }
    ]
  },
  "Ubuntu Linux-26.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "26.04",
        "pkgs": [
          {"reference": "libxml2-16"},
          {"reference": "libxml2-dev"},
          {"reference": "libxml2-doc"},
          {"reference": "libxml2-source"},
          {"reference": "libxml2-utils"},
          {"reference": "python3-libxml2"}
        ]
      }
    ]
  },
  "Red Hat Enterprise Linux-10": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "10",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-devel"},
          {"reference": "libxml2-static"},
          {"reference": "podman"},
          {"reference": "podman-docker"},
          {"reference": "podman-remote"},
          {"reference": "podman-tests"},
          {"reference": "python3-libxml2"}
        ]
      }
    ]
  },
  "CentOS Linux-8": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "8",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-devel"},
          {"reference": "podman"},
          {"reference": "podman-catatonit"},
          {"reference": "podman-docker"},
          {"reference": "podman-gvproxy"},
          {"reference": "podman-manpages"},
          {"reference": "podman-plugins"},
          {"reference": "podman-remote"},
          {"reference": "podman-tests"},
          {"reference": "python3-libxml2"}
        ]
      }
    ]
  },
  "Red Hat Enterprise Linux-8": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "8",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-devel"},
          {"reference": "podman"},
          {"reference": "podman-catatonit"},
          {"reference": "podman-docker"},
          {"reference": "podman-gvproxy"},
          {"reference": "podman-manpages"},
          {"reference": "podman-plugins"},
          {"reference": "podman-remote"},
          {"reference": "podman-tests"},
          {"reference": "python3-libxml2"}
        ]
      }
    ]
  },
  "Red Hat Enterprise Linux-9": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "9",
        "pkgs": [
          {"reference": "libxml2"},
          {"reference": "libxml2-devel"},
          {"reference": "podman"},
          {"reference": "podman-catatonit"},
          {"reference": "podman-docker"},
          {"reference": "podman-gvproxy"},
          {"reference": "podman-plugins"},
          {"reference": "podman-remote"},
          {"reference": "podman-tests"},
          {"reference": "python3-libxml2"}
        ]
      }
    ]
  }
};

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_NOTE,
      extra      : report
  );
  exit(0);
}
else
{
  audit(AUDIT_HOST_NOT, 'affected');
}