CentOS Linux 6 [TuxCare] Security Update: expat / expat-devel Multiple Vulnerabilities (CENTOS6:CLSA-2026:1777304792)

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

include('compat.inc');

if (description)
{
  script_id(361841);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/01");

  script_cve_id("CVE-2017-9233", "CVE-2018-20843", "CVE-2019-15903");
  script_xref(name:"CLSA", value:"2026:1777304792");

  script_name(english:"CentOS Linux 6 [TuxCare] Security Update: expat / expat-devel Multiple Vulnerabilities (CENTOS6:CLSA-2026:1777304792)");

  script_set_attribute(attribute:"synopsis", value:
"The CentOS Linux host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The CentOS Linux 6 host has packages installed that are affected by multiple vulnerabilities as referenced in the
TuxCare CENTOS6:CLSA-2026:1777304792 advisory.

  - In libexpat in Expat before 2.2.7, XML input including XML names that contain a large number of colons
    could make the XML parser consume a high amount of RAM and CPU resources while processing (enough to be
    usable for denial-of-service attacks). (CVE-2018-20843)

  - In libexpat before 2.2.8, crafted XML input could fool the parser into changing from DTD parsing to
    document parsing too early; a consecutive call to XML_GetCurrentLineNumber (or XML_GetCurrentColumnNumber)
    then resulted in a heap-based buffer over-read. (CVE-2019-15903)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version
number.");
  # https://security.tuxcare.com/csaf/v2/els_os/centos6els/advisories/2026/clsa-2026_1777304792.json
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?3c5fa240");
  script_set_attribute(attribute:"see_also", value:"https://cve.tuxcare.com/els/releases/CLSA-2026:1777304792");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages based on the guidance in TuxCare advisory CENTOS6:CLSA-2026:1777304792.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2018-20843");
  script_set_attribute(attribute:"cvss3_score_source", value:"CVE-2019-15903");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2019/06/24");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/04/27");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/01");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

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

  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");
  script_require_keys("Host/OS/extended-third-party", "Host/local_checks_enabled", "Host/CentOS/release", "Host/CentOS/rpm-list");

  exit(0);
}
include('rpm2.inc');

var third_party_support = get_kb_item('Host/OS/extended-third-party');
if (empty_or_null(third_party_support) || third_party_support != 'TuxCare') exit(0, 'TuxCare support not enabled.');

if (!get_kb_item('Host/local_checks_enabled')) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_product = get_kb_item('installed_os/local/SSH/0/product');
if (isnull(os_product) || 'CentOS Linux' >!< os_product) audit(AUDIT_OS_NOT, 'CentOS Linux');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'CentOS Linux');
if (! preg(pattern:"^6([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'CentOS Linux 6', 'CentOS Linux ' + os_version);

if (!get_kb_item('Host/CentOS/rpm-list')) audit(AUDIT_PACKAGE_LIST_MISSING);

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


var constraints = [
  {
    'release': '6',
    'pkgs': [
      {'reference':'expat-2.0.1-13.el6_8.tuxcare.els8', 'cpu':'i686', 'el_string':'el6_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'expat-2.0.1-13.el6_8.tuxcare.els8', 'cpu':'x86_64', 'el_string':'el6_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'expat-devel-2.0.1-13.el6_8.tuxcare.els8', 'cpu':'i686', 'el_string':'el6_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'expat-devel-2.0.1-13.el6_8.tuxcare.els8', 'cpu':'x86_64', 'el_string':'el6_8', 'rpm_spec_vers_cmp':TRUE}
    ]
  }
];

var os_release = get_one_kb_item('installed_os/local/SSH/0/release');
var os_sp = get_one_kb_item('Host/*/minor_release');

var flag = 0;
var reference;
var sp;
var _cpu;
var el_string;
var rpm_spec_vers_cmp;
var epoch;
var allowmaj;
var exists_check;
var cves;
foreach var constraint ( constraints ) {
  # Check that the target release is equal to the affected release
  if (!empty_or_null(constraint['release'])){
    if (constraint['release'] != os_release) continue;
  }
  if (!empty_or_null(constraint['sp'])){
    if (constraint['sp'] != os_sp) continue;
  }
  foreach var pkg ( constraint['pkgs'] ) {
    reference = NULL;
    sp = NULL;
    _cpu = NULL;
    el_string = NULL;
    rpm_spec_vers_cmp = NULL;
    epoch = NULL;
    allowmaj = NULL;
    exists_check = NULL;
    cves = NULL;
    if (!empty_or_null(pkg['reference'])) reference = pkg['reference'];
    if (!empty_or_null(pkg['sp'])) sp = pkg['sp'];
    if (!empty_or_null(pkg['cpu'])) _cpu = pkg['cpu'];
    if (!empty_or_null(pkg['el_string'])) el_string = pkg['el_string'];
    if (!empty_or_null(pkg['rpm_spec_vers_cmp'])) rpm_spec_vers_cmp = pkg['rpm_spec_vers_cmp'];
    if (!empty_or_null(pkg['epoch'])) epoch = pkg['epoch'];
    if (!empty_or_null(pkg['allowmaj'])) allowmaj = pkg['allowmaj'];
    if (!empty_or_null(pkg['exists_check'])) exists_check = pkg['exists_check'];
    if (!empty_or_null(pkg['cves'])) cves = pkg['cves'];
    if (reference &&
        ## (no known rpm to check OR known rpm_exists)
        (!exists_check || rpm_exists(rpm:exists_check)) &&
        rpm_check(sp:sp, cpu:_cpu, reference:reference, epoch:epoch, el_string:el_string, rpm_spec_vers_cmp:rpm_spec_vers_cmp, allowmaj:allowmaj, cves:cves)) flag++;
  }
}


if (flag)
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_HOLE,
      extra      : rpm_report_get()
  );
  exit(0);
}
else
{
  var tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'expat / expat-devel');
}