Ubuntu 16.04 ESM / 18.04 ESM : OpenSSH vulnerabilities (USN-6560-2)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-6560-2. 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(187955);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/08/27");

  script_cve_id("CVE-2023-48795", "CVE-2023-51385");
  script_xref(name:"IAVA", value:"2023-A-0703");
  script_xref(name:"USN", value:"6560-2");
  script_xref(name:"IAVA", value:"2023-A-0701-S");

  script_name(english:"Ubuntu 16.04 ESM / 18.04 ESM : OpenSSH vulnerabilities (USN-6560-2)");

  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 ESM / 18.04 ESM host has packages installed that are affected by multiple vulnerabilities as
referenced in the USN-6560-2 advisory.

    USN-6560-1 fixed several vulnerabilities in OpenSSH. This update provides the corresponding update for
    Ubuntu 16.04 LTS and Ubuntu 18.04 LTS.

    Original advisory details:

    Fabian Bumer, Marcus Brinkmann, Jrg Schwenk discovered that the SSH

    protocol was vulnerable to a prefix truncation attack. If a remote attacker

    was able to intercept SSH communications, extension negotiation messages

    could be truncated, possibly leading to certain algorithms and features

    being downgraded. This issue is known as the Terrapin attack. This update

    adds protocol extensions to mitigate this issue. (CVE-2023-48795)

    It was discovered that OpenSSH incorrectly handled user names or host names

    with shell metacharacters. An attacker could possibly use this issue to

    perform OS command injection. This only affected Ubuntu 18.04 LTS. (CVE-2023-51385)

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-6560-2");
  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:N");
  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:L/I:L/A:N");
  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:H/VI:H/VA:H/SC:N/SI:N/SA:N");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2023-51385");
  script_set_attribute(attribute:"cvss4_score_source", value:"CVE-2023-48795");

  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:"2023/12/18");
  script_set_attribute(attribute:"patch_publication_date", value:"2024/01/11");
  script_set_attribute(attribute:"plugin_publication_date", value:"2024/01/11");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04:-:esm");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:esm");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-client");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-client-ssh1");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-server");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:openssh-sftp-server");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:ssh");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:ssh-askpass-gnome");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:ssh-krb5");
  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) 2024 Canonical, Inc. / NASL script (C) 2024 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl", "ubuntu_pro_sub_detect.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)) audit(AUDIT_OS_NOT, 'Ubuntu 16.04 / 18.04', '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 ubuntu_pro_detected = get_kb_item('Host/Ubuntu/Pro/Services/esm-apps');
ubuntu_pro_detected = !empty_or_null(ubuntu_pro_detected);

var pro_caveat_needed = FALSE;

var pkgs = [
    {'osver': '16.04', 'pkgname': 'openssh-client', 'pkgver': '1:7.2p2-4ubuntu2.10+esm5', 'ubuntu_pro': TRUE},
    {'osver': '16.04', 'pkgname': 'openssh-client-ssh1', 'pkgver': '1:7.2p2-4ubuntu2.10+esm5', 'ubuntu_pro': TRUE},
    {'osver': '16.04', 'pkgname': 'openssh-server', 'pkgver': '1:7.2p2-4ubuntu2.10+esm5', 'ubuntu_pro': TRUE},
    {'osver': '16.04', 'pkgname': 'openssh-sftp-server', 'pkgver': '1:7.2p2-4ubuntu2.10+esm5', 'ubuntu_pro': TRUE},
    {'osver': '16.04', 'pkgname': 'ssh', 'pkgver': '1:7.2p2-4ubuntu2.10+esm5', 'ubuntu_pro': TRUE},
    {'osver': '16.04', 'pkgname': 'ssh-askpass-gnome', 'pkgver': '1:7.2p2-4ubuntu2.10+esm5', 'ubuntu_pro': TRUE},
    {'osver': '16.04', 'pkgname': 'ssh-krb5', 'pkgver': '1:7.2p2-4ubuntu2.10+esm5', 'ubuntu_pro': TRUE},
    {'osver': '18.04', 'pkgname': 'openssh-client', 'pkgver': '1:7.6p1-4ubuntu0.7+esm3', 'ubuntu_pro': TRUE},
    {'osver': '18.04', 'pkgname': 'openssh-server', 'pkgver': '1:7.6p1-4ubuntu0.7+esm3', 'ubuntu_pro': TRUE},
    {'osver': '18.04', 'pkgname': 'openssh-sftp-server', 'pkgver': '1:7.6p1-4ubuntu0.7+esm3', 'ubuntu_pro': TRUE},
    {'osver': '18.04', 'pkgname': 'ssh', 'pkgver': '1:7.6p1-4ubuntu0.7+esm3', 'ubuntu_pro': TRUE},
    {'osver': '18.04', 'pkgname': 'ssh-askpass-gnome', 'pkgver': '1:7.6p1-4ubuntu0.7+esm3', 'ubuntu_pro': TRUE}
];

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'];
  var pro_required = NULL;
  if (!empty_or_null(package_array['ubuntu_pro'])) pro_required = package_array['ubuntu_pro'];
  if (osver && pkgname && pkgver) {
    if (ubuntu_check(osver:osver, pkgname:pkgname, pkgver:pkgver)) {
        flag++;
        if (!ubuntu_pro_detected && !pro_caveat_needed) pro_caveat_needed = pro_required;
    }
  }
}

if (flag)
{
  var extra = '';
  if (pro_caveat_needed) {
    extra += 'NOTE: This vulnerability check contains fixes that apply to packages only \n';
    extra += 'available in Ubuntu ESM repositories. Access to these package security updates \n';
    extra += 'require an Ubuntu Pro subscription.\n\n';
  }
  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, 'openssh-client / openssh-client-ssh1 / openssh-server / etc');
}