Alibaba Cloud Linux 3 : 0047: libxml2 (ALINUX3-SA-2021:0047)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The package checks in this plugin were extracted from
# Alibaba Cloud Linux Security Advisory ALINUX3-SA-2021:0047.
##

include('compat.inc');

if (description)
{
  script_id(236735);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2025/05/14");

  script_cve_id(
    "CVE-2021-3516",
    "CVE-2021-3517",
    "CVE-2021-3518",
    "CVE-2021-3537",
    "CVE-2021-3541"
  );

  script_name(english:"Alibaba Cloud Linux 3 : 0047: libxml2 (ALINUX3-SA-2021:0047)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Alibaba Cloud Linux host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The remote Alibaba Cloud Linux 3 host has packages installed that are affected by multiple vulnerabilities as referenced
in the ALINUX3-SA-2021:0047 advisory.

    Package updates are available for Alibaba Cloud Linux 3 that fix the following vulnerabilities:

    CVE-2021-3516:
    There's a flaw in libxml2's xmllint in versions before 2.9.11. An attacker who is able to submit a crafted
    file to be processed by xmllint could trigger a use-after-free. The greatest impact of this flaw is to
    confidentiality, integrity, and availability.

    CVE-2021-3517:
    There is a flaw in the xml entity encoding functionality of libxml2 in versions before 2.9.11. An attacker
    who is able to supply a crafted file to be processed by an application linked with the affected
    functionality of libxml2 could trigger an out-of-bounds read. The most likely impact of this flaw is to
    application availability, with some potential impact to confidentiality and integrity if an attacker is
    able to use memory information to further exploit the application.

    CVE-2021-3518:
    There's a flaw in libxml2 in versions before 2.9.11. An attacker who is able to submit a crafted file to
    be processed by an application linked with libxml2 could trigger a use-after-free. The greatest impact
    from this flaw is to confidentiality, integrity, and availability.

    CVE-2021-3537:
    A vulnerability found in libxml2 in versions before 2.9.11 shows that it did not propagate errors while
    parsing XML mixed content, causing a NULL dereference. If an untrusted XML document was parsed in recovery
    mode and post-validated, the flaw could be used to crash the application. The highest threat from this
    vulnerability is to system availability.

    CVE-2021-3541:
    A flaw was found in libxml2. Exponential entity expansion attack its possible bypassing all existing
    protection mechanisms and leading to denial of service.

Tenable has extracted the preceding description block directly from the Alibaba Cloud Linux 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:"http://mirrors.aliyun.com/alinux/3/cve/alinux3-sa-20210047.xml");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages.");
  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:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:R/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:"cvss_score_source", value:"CVE-2021-3517");
  script_set_attribute(attribute:"cvss3_score_source", value:"CVE-2021-3518");

  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:"2021/05/14");
  script_set_attribute(attribute:"patch_publication_date", value:"2021/07/14");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/05/14");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:libxml2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:libxml2-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:libxml2-debugsource");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:libxml2-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:libxml2-static");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:python3-libxml2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:python3-libxml2-debuginfo");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:alibabacloud:alibaba_cloud_linux_3");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Alibaba Cloud Linux Local Security Checks");

  script_copyright(english:"This script is Copyright (C) 2025 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/Alibaba/release", "Host/Alibaba/rpm-list", "Host/cpu");

  exit(0);
}


include('rpm.inc');

if (!get_kb_item('Host/local_checks_enabled')) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_release = get_kb_item('Host/Alibaba/release');
if (isnull(os_release) || 'Alibaba Cloud Linux' >!< os_release) audit(AUDIT_OS_NOT, 'Alibaba Cloud Linux');
var os_ver = pregmatch(pattern: "Alibaba Cloud Linux release ([0-9]+(\.[0-9]+)?)", string:os_release);
if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, 'Alibaba Cloud Linux');
os_ver = os_ver[1];
if (! preg(pattern:"^3([^0-9]|$)", string:os_ver)) audit(AUDIT_OS_NOT, 'Alibaba Cloud Linux 3.x', 'Alibaba Cloud Linux ' + os_ver);

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

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('aarch64' >!< cpu && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Alibaba Cloud Linux', cpu);

var pkgs = [
    {'reference':'libxml2-2.9.7-9.1.al8.2', 'cpu':'aarch64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'libxml2-2.9.7-9.1.al8.2', 'cpu':'x86_64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'libxml2-debuginfo-2.9.7-9.1.al8.2', 'cpu':'aarch64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'libxml2-debuginfo-2.9.7-9.1.al8.2', 'cpu':'x86_64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'libxml2-debugsource-2.9.7-9.1.al8.2', 'cpu':'aarch64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'libxml2-debugsource-2.9.7-9.1.al8.2', 'cpu':'x86_64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'libxml2-devel-2.9.7-9.1.al8.2', 'cpu':'aarch64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'libxml2-devel-2.9.7-9.1.al8.2', 'cpu':'x86_64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'libxml2-static-2.9.7-9.1.al8.2', 'cpu':'aarch64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'libxml2-static-2.9.7-9.1.al8.2', 'cpu':'x86_64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'python3-libxml2-2.9.7-9.1.al8.2', 'cpu':'aarch64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'python3-libxml2-2.9.7-9.1.al8.2', 'cpu':'x86_64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'python3-libxml2-debuginfo-2.9.7-9.1.al8.2', 'cpu':'aarch64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
    {'reference':'python3-libxml2-debuginfo-2.9.7-9.1.al8.2', 'cpu':'x86_64', 'release':'3', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'}
];

var flag = 0;
foreach var package_array ( pkgs ) {
  var reference = NULL;
  var _release = NULL;
  var sp = NULL;
  var _cpu = NULL;
  var el_string = NULL;
  var rpm_spec_vers_cmp = NULL;
  var epoch = NULL;
  var allowmaj = NULL;
  var exists_check = NULL;
  var cves = NULL;
  if (!empty_or_null(package_array['reference'])) reference = package_array['reference'];
  if (!empty_or_null(package_array['release'])) _release = 'Alibaba Linux ' + package_array['release'];
  if (!empty_or_null(package_array['sp'])) sp = package_array['sp'];
  if (!empty_or_null(package_array['cpu'])) _cpu = package_array['cpu'];
  if (!empty_or_null(package_array['el_string'])) el_string = package_array['el_string'];
  if (!empty_or_null(package_array['rpm_spec_vers_cmp'])) rpm_spec_vers_cmp = package_array['rpm_spec_vers_cmp'];
  if (!empty_or_null(package_array['epoch'])) epoch = package_array['epoch'];
  if (!empty_or_null(package_array['allowmaj'])) allowmaj = package_array['allowmaj'];
  if (!empty_or_null(package_array['exists_check'])) exists_check = package_array['exists_check'];
  if (!empty_or_null(package_array['cves'])) cves = package_array['cves'];
  if (reference && _release && (!exists_check || rpm_exists(release:_release, rpm:exists_check))) {
    if (rpm_check(release:_release, 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, 'libxml2 / libxml2-debuginfo / libxml2-debugsource / libxml2-devel / etc');
}