Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : LibVNCServer vulnerabilities (USN-4407-1)

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-4407-1. The text 
# itself is copyright (C) Canonical, Inc. See 
# <http://www.ubuntu.com/usn/>. Ubuntu(R) is a registered 
# trademark of Canonical, Inc.
#

include('compat.inc');

if (description)
{
  script_id(138132);
  script_version("1.9");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/08/27");

  script_cve_id(
    "CVE-2017-18922",
    "CVE-2019-15680",
    "CVE-2019-15681",
    "CVE-2019-15690",
    "CVE-2019-20788"
  );
  script_xref(name:"USN", value:"4407-1");
  script_xref(name:"IAVA", value:"2020-A-0381");

  script_name(english:"Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : LibVNCServer vulnerabilities (USN-4407-1)");

  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 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple
vulnerabilities as referenced in the USN-4407-1 advisory.

    It was discovered that LibVNCServer incorrectly handled decompressing data. An attacker could possibly use
    this issue to cause LibVNCServer to crash, resulting in a denial of service. (CVE-2019-15680)

    It was discovered that an information disclosure vulnerability existed in LibVNCServer when sending a
    ServerCutText message. An attacker could possibly use this issue to expose sensitive information. This
    issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2019-15681)

    It was discovered that LibVNCServer incorrectly handled cursor shape updates. If a user were tricked in to
    connecting to a malicious server, an attacker could possibly use this issue to cause LibVNCServer to
    crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected
    Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2019-15690, CVE-2019-20788)

    It was discovered that LibVNCServer incorrectly handled decoding WebSocket frames. An attacker could
    possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly
    execute arbitrary code. This issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS.
    (CVE-2017-18922)

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-4407-1");
  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: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:"cvss_score_source", value:"CVE-2019-20788");

  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:"2019/10/29");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/07/01");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/07/06");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libvncclient1");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libvncserver-config");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libvncserver-dev");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libvncserver1");
  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:"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) 2020-2024 Canonical, Inc. / NASL script (C) 2020-2024 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 (! ('16.04' >< os_release || '18.04' >< os_release || '20.04' >< os_release)) audit(AUDIT_OS_NOT, 'Ubuntu 16.04 / 18.04 / 20.04', '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': '16.04', 'pkgname': 'libvncclient1', 'pkgver': '0.9.10+dfsg-3ubuntu0.16.04.4'},
    {'osver': '16.04', 'pkgname': 'libvncserver-config', 'pkgver': '0.9.10+dfsg-3ubuntu0.16.04.4'},
    {'osver': '16.04', 'pkgname': 'libvncserver-dev', 'pkgver': '0.9.10+dfsg-3ubuntu0.16.04.4'},
    {'osver': '16.04', 'pkgname': 'libvncserver1', 'pkgver': '0.9.10+dfsg-3ubuntu0.16.04.4'},
    {'osver': '18.04', 'pkgname': 'libvncclient1', 'pkgver': '0.9.11+dfsg-1ubuntu1.2'},
    {'osver': '18.04', 'pkgname': 'libvncserver-config', 'pkgver': '0.9.11+dfsg-1ubuntu1.2'},
    {'osver': '18.04', 'pkgname': 'libvncserver-dev', 'pkgver': '0.9.11+dfsg-1ubuntu1.2'},
    {'osver': '18.04', 'pkgname': 'libvncserver1', 'pkgver': '0.9.11+dfsg-1ubuntu1.2'},
    {'osver': '20.04', 'pkgname': 'libvncclient1', 'pkgver': '0.9.12+dfsg-9ubuntu0.1'},
    {'osver': '20.04', 'pkgname': 'libvncserver-dev', 'pkgver': '0.9.12+dfsg-9ubuntu0.1'},
    {'osver': '20.04', 'pkgname': 'libvncserver1', 'pkgver': '0.9.12+dfsg-9ubuntu0.1'}
];

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 (osver && pkgname && pkgver) {
    if (ubuntu_check(osver:osver, pkgname:pkgname, pkgver:pkgver)) flag++;
  }
}

if (flag)
{
  var extra = '';
  extra += ubuntu_report_get();
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    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, 'libvncclient1 / libvncserver-config / libvncserver-dev / etc');
}