Ubuntu 16.04 LTS / 18.04 LTS : Linux kernel vulnerabilities (USN-4749-1)

##
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-4749-1. 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(147983);
  script_version("1.7");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/01/09");

  script_cve_id(
    "CVE-2020-25669",
    "CVE-2020-27815",
    "CVE-2020-27830",
    "CVE-2020-28941",
    "CVE-2020-29374",
    "CVE-2020-29568",
    "CVE-2020-29569",
    "CVE-2020-29660",
    "CVE-2020-29661"
  );
  script_xref(name:"USN", value:"4749-1");

  script_name(english:"Ubuntu 16.04 LTS / 18.04 LTS : Linux kernel vulnerabilities (USN-4749-1)");

  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 host has a package installed that is affected by multiple vulnerabilities as
referenced in the USN-4749-1 advisory.

  - A vulnerability was found in the Linux Kernel where the function sunkbd_reinit having been scheduled by
    sunkbd_interrupt before sunkbd being freed. Though the dangling pointer is set to NULL in
    sunkbd_disconnect, there is still an alias in sunkbd_reinit causing Use After Free. (CVE-2020-25669)

  - A flaw was found in the JFS filesystem code in the Linux Kernel which allows a local attacker with the
    ability to set extended attributes to panic the system, causing memory corruption or escalating
    privileges. The highest threat from this vulnerability is to confidentiality, integrity, as well as system
    availability. (CVE-2020-27815)

  - A vulnerability was found in Linux Kernel where in the spk_ttyio_receive_buf2() function, it would
    dereference spk_ttyio_synth without checking whether it is NULL or not, and may lead to a NULL-ptr deref
    crash. (CVE-2020-27830)

  - An issue was discovered in drivers/accessibility/speakup/spk_ttyio.c in the Linux kernel through 5.9.9.
    Local attackers on systems with the speakup driver could cause a local denial of service attack, aka
    CID-d41227544427. This occurs because of an invalid free when the line discipline is used more than once.
    (CVE-2020-28941)

  - An issue was discovered in the Linux kernel before 5.7.3, related to mm/gup.c and mm/huge_memory.c. The
    get_user_pages (aka gup) implementation, when used for a copy-on-write page, does not properly consider
    the semantics of read operations and therefore can grant unintended write access, aka CID-17839856fd58.
    (CVE-2020-29374)

  - An issue was discovered in Xen through 4.14.x. Some OSes (such as Linux, FreeBSD, and NetBSD) are
    processing watch events using a single thread. If the events are received faster than the thread is able
    to handle, they will get queued. As the queue is unbounded, a guest may be able to trigger an OOM in the
    backend. All systems with a FreeBSD, Linux, or NetBSD (any version) dom0 are vulnerable. (CVE-2020-29568)

  - An issue was discovered in the Linux kernel through 5.10.1, as used with Xen through 4.14.x. The Linux
    kernel PV block backend expects the kernel thread handler to reset ring->xenblkd to NULL when stopped.
    However, the handler may not have time to run if the frontend quickly toggles between the states connect
    and disconnect. As a consequence, the block backend may re-use a pointer after it was freed. A misbehaving
    guest can trigger a dom0 crash by continuously connecting / disconnecting a block frontend. Privilege
    escalation and information leaks cannot be ruled out. This only affects systems with a Linux blkback.
    (CVE-2020-29569)

  - A locking inconsistency issue was discovered in the tty subsystem of the Linux kernel through 5.9.13.
    drivers/tty/tty_io.c and drivers/tty/tty_jobctrl.c may allow a read-after-free attack against TIOCGSID,
    aka CID-c8bcd9c5be24. (CVE-2020-29660)

  - A locking issue was discovered in the tty subsystem of the Linux kernel through 5.9.13.
    drivers/tty/tty_jobctrl.c allows a use-after-free attack against TIOCSPGRP, aka CID-54ffccbf053b.
    (CVE-2020-29661)

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-4749-1");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/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:C/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-2020-29661");
  script_set_attribute(attribute:"cvss3_score_source", value:"CVE-2020-29569");

  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:"2020/11/19");
  script_set_attribute(attribute:"patch_publication_date", value:"2021/02/25");
  script_set_attribute(attribute:"plugin_publication_date", value:"2021/03/23");

  script_set_attribute(attribute:"plugin_type", value:"local");
  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:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1012-dell300x");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1065-oracle");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1079-gke");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1079-raspi2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1085-kvm");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1093-gcp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1094-aws");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1096-snapdragon");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1108-azure");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-136-generic");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-136-generic-lpae");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-136-lowlatency");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

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

  script_copyright(english:"Ubuntu Security Notice (C) 2021-2024 Canonical, Inc. / NASL script (C) 2021-2024 and is owned by Tenable, Inc. or an Affiliate thereof.");

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

  exit(0);
}

include('debian_package.inc');
include('ksplice.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 kernel_mappings = {
  '16.04': {
    '4.15.0': {
      'generic': '4.15.0-136',
      'generic-lpae': '4.15.0-136',
      'lowlatency': '4.15.0-136',
      'oracle': '4.15.0-1065',
      'gcp': '4.15.0-1093',
      'aws': '4.15.0-1094',
      'azure': '4.15.0-1108'
    }
  },
  '18.04': {
    '4.15.0': {
      'generic': '4.15.0-136',
      'generic-lpae': '4.15.0-136',
      'lowlatency': '4.15.0-136',
      'dell300x': '4.15.0-1012',
      'oracle': '4.15.0-1065',
      'gke': '4.15.0-1079',
      'raspi2': '4.15.0-1079',
      'kvm': '4.15.0-1085',
      'gcp': '4.15.0-1093',
      'aws': '4.15.0-1094',
      'snapdragon': '4.15.0-1096',
      'azure': '4.15.0-1108'
    }
  }
};

var host_kernel_release = get_kb_item('Host/uptrack-uname-r');
if (empty_or_null(host_kernel_release)) host_kernel_release = get_kb_item_or_exit('Host/uname-r');
var host_kernel_base_version = get_kb_item_or_exit('Host/Debian/kernel-base-version');
var host_kernel_type = get_kb_item_or_exit('Host/Debian/kernel-type');
if(empty_or_null(kernel_mappings[os_release][host_kernel_base_version][host_kernel_type])) audit(AUDIT_INST_VER_NOT_VULN, 'kernel ' + host_kernel_release);

var extra = '';
var kernel_fixed_version = kernel_mappings[os_release][host_kernel_base_version][host_kernel_type] + "-" + host_kernel_type;
if (deb_ver_cmp(ver1:host_kernel_release, ver2:kernel_fixed_version) < 0)
{
  extra = extra + 'Running Kernel level of ' + host_kernel_release + ' does not meet the minimum fixed level of ' + kernel_fixed_version + ' for this advisory.\n\n';
}
  else
{
  audit(AUDIT_PATCH_INSTALLED, 'Kernel package for USN-4749-1');
}

if (get_one_kb_item('Host/ksplice/kernel-cves'))
{
  var cve_list = make_list('CVE-2020-25669', 'CVE-2020-27815', 'CVE-2020-27830', 'CVE-2020-28941', 'CVE-2020-29374', 'CVE-2020-29568', 'CVE-2020-29569', 'CVE-2020-29660', 'CVE-2020-29661');
  if (ksplice_cves_check(cve_list))
  {
    audit(AUDIT_PATCH_INSTALLED, 'KSplice hotfix for USN-4749-1');
  }
  else
  {
    extra = extra + ksplice_reporting_text();
  }
}
if (extra) {
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : extra
  );
  exit(0);
}