Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS : Expat vulnerabilities (USN-8813-1)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-8813-1. The text
# itself is copyright (C) Canonical, Inc. See
# <https://ubuntu.com/security/notices>. Ubuntu(R) is a registered
# trademark of Canonical, Inc.
##

include('compat.inc');

if (description)
{
  script_id(350173);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/25");

  script_cve_id(
    "CVE-2026-56131",
    "CVE-2026-56132",
    "CVE-2026-56406",
    "CVE-2026-56407",
    "CVE-2026-56409",
    "CVE-2026-56410",
    "CVE-2026-56411",
    "CVE-2026-66046",
    "CVE-2026-72522",
    "CVE-2026-76641",
    "CVE-2026-76957"
  );
  script_xref(name:"IAVA", value:"2026-A-0650-S");
  script_xref(name:"IAVA", value:"2026-A-0899-S");
  script_xref(name:"IAVA", value:"2026-A-0925-S");
  script_xref(name:"USN", value:"8813-1");

  script_name(english:"Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS : Expat vulnerabilities (USN-8813-1)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Ubuntu host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The remote Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS host has packages
installed that are affected by multiple vulnerabilities as referenced in the USN-8813-1 advisory.

    It was discovered that Expat did not correctly handle certain integer arithmetic. An attacker could
    possibly use this issue to cause a denial of service.

    (CVE-2026-56406, CVE-2026-56407, CVE-2026-56409, CVE-2026-56410, CVE-2026-56411)

    It was discovered that Expat did not correctly track handler call depth. An attacker could possibly use
    this issue to cause Expat to crash or execute arbitrary code. (CVE-2026-56131)

    It was discovered that Expat did not correctly handle certain memory operations. An attacker could
    possibly use this issue to cause Expat to crash or execute arbitrary code. (CVE-2026-56132)

    It was discovered that Expat did not correctly handle certain Unicode characters. An attacker could
    possibly use this issue to cause Expat to use excessive resources, leading to a denial of service.
    (CVE-2026-72522)

    It was discovered that Expat did not correctly process certain XML attributes. A remote attacker could
    possibly use this issue to cause Expat to use excessive resources, leading to a denial of service.
    (CVE-2026-66046)

    It was discovered that Expat did not correctly handle certain external entities. An attacker could
    possibly use this issue to cause Expat to crash or execute arbitrary code. (CVE-2026-76641)

    It was discovered that Expat did not correctly track handler call depth with custom encodings. An attacker
    could possibly use this issue to cause Expat to crash or execute arbitrary code. (CVE-2026-76957)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/notices/USN-8813-1");
  script_set_attribute(attribute:"solution", value:
"Update the affected expat, lib64expat1 and / or libexpat1 packages.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss4_vector", value:"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:P");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-76957");
  script_set_attribute(attribute:"cvss4_score_source", value:"CVE-2026-76641");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/06/19");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/09/24");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/25");

  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:"p-cpe:/a:canonical:ubuntu_linux:expat");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:lib64expat1");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libexpat1");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_set_attribute(attribute:"stig_severity", value:"I");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Ubuntu Local Security Checks");

  script_copyright(english:"Ubuntu Security Notice (C) 2026 Canonical, Inc. / NASL script (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/cpu", "Host/Ubuntu", "Host/Ubuntu/release", "Host/Debian/dpkg-l");

  exit(0);
}

include('debian_package.inc');

if ( ! get_kb_item('Host/local_checks_enabled') ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_release = get_kb_item('Host/Ubuntu/release');
if ( isnull(os_release) ) audit(AUDIT_OS_NOT, 'Ubuntu');
os_release = chomp(os_release);
if (! ('14.04' >< os_release || '16.04' >< os_release || '18.04' >< os_release || '20.04' >< os_release || '22.04' >< os_release || '24.04' >< os_release || '26.04' >< os_release)) audit(AUDIT_OS_NOT, 'Ubuntu 14.04 / 16.04 / 18.04 / 20.04 / 22.04 / 24.04 / 26.04', 'Ubuntu ' + os_release);
if ( ! get_kb_item('Host/Debian/dpkg-l') ) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 's390' >!< cpu && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Ubuntu', cpu);

var pkgs = [
    {'osver': '14.04', 'pkgname': 'expat', 'pkgver': '2.1.0-4ubuntu1.4+esm13'},
    {'osver': '14.04', 'pkgname': 'lib64expat1', 'pkgver': '2.1.0-4ubuntu1.4+esm13'},
    {'osver': '14.04', 'pkgname': 'libexpat1', 'pkgver': '2.1.0-4ubuntu1.4+esm13'},
    {'osver': '16.04', 'pkgname': 'expat', 'pkgver': '2.1.0-7ubuntu0.16.04.5+esm14'},
    {'osver': '16.04', 'pkgname': 'lib64expat1', 'pkgver': '2.1.0-7ubuntu0.16.04.5+esm14'},
    {'osver': '16.04', 'pkgname': 'libexpat1', 'pkgver': '2.1.0-7ubuntu0.16.04.5+esm14'},
    {'osver': '18.04', 'pkgname': 'expat', 'pkgver': '2.2.5-3ubuntu0.9+esm5'},
    {'osver': '18.04', 'pkgname': 'libexpat1', 'pkgver': '2.2.5-3ubuntu0.9+esm5'},
    {'osver': '20.04', 'pkgname': 'expat', 'pkgver': '2.2.9-1ubuntu0.8+esm3'},
    {'osver': '20.04', 'pkgname': 'libexpat1', 'pkgver': '2.2.9-1ubuntu0.8+esm3'},
    {'osver': '22.04', 'pkgname': 'expat', 'pkgver': '2.4.7-1ubuntu0.9'},
    {'osver': '22.04', 'pkgname': 'libexpat1', 'pkgver': '2.4.7-1ubuntu0.9'},
    {'osver': '24.04', 'pkgname': 'expat', 'pkgver': '2.6.1-2ubuntu0.6'},
    {'osver': '24.04', 'pkgname': 'libexpat1', 'pkgver': '2.6.1-2ubuntu0.6'},
    {'osver': '26.04', 'pkgname': 'expat', 'pkgver': '2.7.4-1ubuntu0.2'},
    {'osver': '26.04', 'pkgname': 'libexpat1', 'pkgver': '2.7.4-1ubuntu0.2'}
];

var flag = 0;
foreach var package_array ( pkgs ) {
  var osver = NULL;
  var pkgname = NULL;
  var pkgver = NULL;
  if (!empty_or_null(package_array['osver'])) osver = package_array['osver'];
  if (!empty_or_null(package_array['pkgname'])) pkgname = package_array['pkgname'];
  if (!empty_or_null(package_array['pkgver'])) pkgver = package_array['pkgver'];
  if (!empty_or_null(package_array['cves'])) cves = package_array['cves'];
  if (osver && pkgname && pkgver) {
    if (deb_check(release:osver, prefix:pkgname, reference:pkgver, cves:cves)) flag++;
  }
}

if (flag)
{
  var extra = '';
  extra += ubuntu_report_get();
  security_report_v4(
    port       : 0,
    severity   : SECURITY_WARNING,
    extra      : extra
  );
  exit(0);
}
else
{
  var tested = ubuntu_pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'expat / lib64expat1 / libexpat1');
}