Ubuntu 16.04 LTS / 18.04 LTS : Linux kernel vulnerabilities (USN-4485-1)

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-4485-1. 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(140183);
  script_version("1.8");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/01/09");

  script_cve_id(
    "CVE-2018-20669",
    "CVE-2019-19947",
    "CVE-2019-20810",
    "CVE-2020-10732",
    "CVE-2020-10766",
    "CVE-2020-10767",
    "CVE-2020-10768",
    "CVE-2020-10781",
    "CVE-2020-12655",
    "CVE-2020-12656",
    "CVE-2020-12771",
    "CVE-2020-13974",
    "CVE-2020-15393",
    "CVE-2020-24394"
  );
  script_xref(name:"USN", value:"4485-1");

  script_name(english:"Ubuntu 16.04 LTS / 18.04 LTS : Linux kernel vulnerabilities (USN-4485-1)");

  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-4485-1 advisory.

  - An issue where a provided address with access_ok() is not checked was discovered in
    i915_gem_execbuffer2_ioctl in drivers/gpu/drm/i915/i915_gem_execbuffer.c in the Linux kernel through
    4.19.13. A local attacker can craft a malicious IOCTL function call to overwrite arbitrary kernel memory,
    resulting in a Denial of Service or privilege escalation. (CVE-2018-20669)

  - In the Linux kernel through 5.4.6, there are information leaks of uninitialized memory to a USB device in
    the drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c driver, aka CID-da2311a6385c. (CVE-2019-19947)

  - go7007_snd_init in drivers/media/usb/go7007/snd-go7007.c in the Linux kernel before 5.6 does not call
    snd_card_free for a failure path, which causes a memory leak, aka CID-9453264ef586. (CVE-2019-20810)

  - A flaw was found in the Linux kernel's implementation of Userspace core dumps. This flaw allows an
    attacker with a local account to crash a trivial program and exfiltrate private kernel data.
    (CVE-2020-10732)

  - A logic bug flaw was found in Linux kernel before 5.8-rc1 in the implementation of SSBD. A bug in the
    logic handling allows an attacker with a local account to disable SSBD protection during a context switch
    when additional speculative execution mitigations are in place. This issue was introduced when the per
    task/process conditional STIPB switching was added on top of the existing SSBD switching. The highest
    threat from this vulnerability is to confidentiality. (CVE-2020-10766)

  - A flaw was found in the Linux kernel before 5.8-rc1 in the implementation of the Enhanced IBPB (Indirect
    Branch Prediction Barrier). The IBPB mitigation will be disabled when STIBP is not available or when the
    Enhanced Indirect Branch Restricted Speculation (IBRS) is available. This flaw allows a local attacker to
    perform a Spectre V2 style attack when this configuration is active. The highest threat from this
    vulnerability is to confidentiality. (CVE-2020-10767)

  - A flaw was found in the Linux Kernel before 5.8-rc1 in the prctl() function, where it can be used to
    enable indirect branch speculation after it has been disabled. This call incorrectly reports it as being
    'force disabled' when it is not and opens the system to Spectre v2 attacks. The highest threat from this
    vulnerability is to confidentiality. (CVE-2020-10768)

  - A flaw was found in the Linux Kernel before 5.8-rc6 in the ZRAM kernel module, where a user with a local
    account and the ability to read the /sys/class/zram-control/hot_add file can create ZRAM device nodes in
    the /dev/ directory. This read allocates kernel memory and is not accounted for a user that triggers the
    creation of that ZRAM device. With this vulnerability, continually reading the device may consume a large
    amount of system memory and cause the Out-of-Memory (OOM) killer to activate and terminate random
    userspace processes, possibly making the system inoperable. (CVE-2020-10781)

  - An issue was discovered in xfs_agf_verify in fs/xfs/libxfs/xfs_alloc.c in the Linux kernel through 5.6.10.
    Attackers may trigger a sync of excessive duration via an XFS v5 image with crafted metadata, aka
    CID-d0c7feaf8767. (CVE-2020-12655)

  - gss_mech_free in net/sunrpc/auth_gss/gss_mech_switch.c in the rpcsec_gss_krb5 implementation in the Linux
    kernel through 5.6.10 lacks certain domain_release calls, leading to a memory leak. Note: This was
    disputed with the assertion that the issue does not grant any access not already available. It is a
    problem that on unloading a specific kernel module some memory is leaked, but loading kernel modules is a
    privileged operation. A user could also write a kernel module to consume any amount of memory they like
    and load that replicating the effect of this bug (CVE-2020-12656)

  - An issue was discovered in the Linux kernel through 5.6.11. btree_gc_coalesce in drivers/md/bcache/btree.c
    has a deadlock if a coalescing operation fails. (CVE-2020-12771)

  - An issue was discovered in the Linux kernel 4.4 through 5.7.1. drivers/tty/vt/keyboard.c has an integer
    overflow if k_ascii is called several times in a row, aka CID-b86dab054059. NOTE: Members in the community
    argue that the integer overflow does not lead to a security issue in this case. (CVE-2020-13974)

  - In the Linux kernel 4.4 through 5.7.6, usbtest_disconnect in drivers/usb/misc/usbtest.c has a memory leak,
    aka CID-28ebeb8db770. (CVE-2020-15393)

  - In the Linux kernel before 5.7.8, fs/nfsd/vfs.c (in the NFS server) can set incorrect permissions on new
    filesystem objects when the filesystem lacks ACL support, aka CID-22cf8419f131. This occurs because the
    current umask is not considered. (CVE-2020-24394)

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-4485-1");
  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: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-2020-13974");

  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:"2019/03/21");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/09/03");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/09/02");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1051-oracle");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1067-gke");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1068-raspi2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1072-kvm");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1080-aws");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1081-gcp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1084-snapdragon");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1093-azure");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1094-oem");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-115-generic");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-115-generic-lpae");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-115-lowlatency");
  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:"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) 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", "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': {
      'oracle': '4.15.0-1051',
      'aws': '4.15.0-1080',
      'gcp': '4.15.0-1081',
      'azure': '4.15.0-1093'
    }
  },
  '18.04': {
    '4.15.0': {
      'generic': '4.15.0-115',
      'generic-lpae': '4.15.0-115',
      'lowlatency': '4.15.0-115',
      'oracle': '4.15.0-1051',
      'gke': '4.15.0-1067',
      'raspi2': '4.15.0-1068',
      'kvm': '4.15.0-1072',
      'aws': '4.15.0-1080',
      'gcp': '4.15.0-1081',
      'snapdragon': '4.15.0-1084',
      'azure': '4.15.0-1093',
      'oem': '4.15.0-1094'
    }
  }
};

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-4485-1');
}

if (get_one_kb_item('Host/ksplice/kernel-cves'))
{
  var cve_list = make_list('CVE-2018-20669', 'CVE-2019-19947', 'CVE-2019-20810', 'CVE-2020-10732', 'CVE-2020-10766', 'CVE-2020-10767', 'CVE-2020-10768', 'CVE-2020-10781', 'CVE-2020-12655', 'CVE-2020-12656', 'CVE-2020-12771', 'CVE-2020-13974', 'CVE-2020-15393', 'CVE-2020-24394');
  if (ksplice_cves_check(cve_list))
  {
    audit(AUDIT_PATCH_INSTALLED, 'KSplice hotfix for USN-4485-1');
  }
  else
  {
    extra = extra + ksplice_reporting_text();
  }
}
if (extra) {
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : extra
  );
  exit(0);
}