Linux Distros Unpatched Vulnerability : CVE-2021-47072

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(244393);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2025/08/06");

  script_cve_id("CVE-2021-47072");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2021-47072");

  script_set_attribute(attribute:"synopsis", value:
"The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be
patched.");
  script_set_attribute(attribute:"description", value:
"The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied
patch available.

  - In the Linux kernel, the following vulnerability has been resolved: btrfs: fix removed dentries still
    existing after log is synced When we move one inode from one directory to another and both the inode and
    its previous parent directory were logged before, we are not supposed to have the dentry for the old
    parent if we have a power failure after the log is synced. Only the new dentry is supposed to exist.
    Generally this works correctly, however there is a scenario where this is not currently working, because
    the old parent of the file/directory that was moved is not authoritative for a range that includes the dir
    index and dir item keys of the old dentry. This case is better explained with the following example and
    reproducer: # The test requires a very specific layout of keys and items in the # fs/subvolume btree to
    trigger the bug. So we want to make sure that # on whatever platform we are, we have the same leaf/node
    size. # # Currently in btrfs the node/leaf size can not be smaller than the page # size (but it can be
    greater than the page size). So use the largest # supported node/leaf size (64K). $ mkfs.btrfs -f -n 65536
    /dev/sdc $ mount /dev/sdc /mnt # testdir is inode 257. $ mkdir /mnt/testdir $ chmod 755 /mnt/testdir #
    Create several empty files to have the directory testdir with its # items spread over several leaves (7
    in this case). $ for ((i = 1; i <= 1200; i++)); do echo -n > /mnt/testdir/file$i done # Create our test
    directory dira, inode number 1458, which gets all # its items in leaf 7. # # The BTRFS_DIR_ITEM_KEY item
    for inode 257 (testdir) that points to # the entry named dira is in leaf 2, while the
    BTRFS_DIR_INDEX_KEY # item that points to that entry is in leaf 3. # # For this particular filesystem node
    size (64K), file count and file # names, we endup with the directory entry items from inode 257 in #
    leaves 2 and 3, as previously mentioned - what matters for triggering # the bug exercised by this test
    case is that those items are not placed # in leaf 1, they must be placed in a leaf different from the one
    # containing the inode item for inode 257. # # The corresponding BTRFS_DIR_ITEM_KEY and
    BTRFS_DIR_INDEX_KEY items for # the parent inode (257) are the following: # # item 460 key (257 DIR_ITEM
    3724298081) itemoff 48344 itemsize 34 # location key (1458 INODE_ITEM 0) type DIR # transid 6 data_len 0
    name_len 4 # name: dira # # and: # # item 771 key (257 DIR_INDEX 1202) itemoff 36673 itemsize 34 #
    location key (1458 INODE_ITEM 0) type DIR # transid 6 data_len 0 name_len 4 # name: dira $ mkdir
    /mnt/testdir/dira # Make sure everything done so far is durably persisted. $ sync # Now do a change to
    inode 257 (testdir) that does not result in # COWing leaves 2 and 3 - the leaves that contain the
    directory items # pointing to inode 1458 (directory dira). # # Changing permissions, the owner/group,
    updating or adding a xattr, # etc, will not change (COW) leaves 2 and 3. So for the sake of # simplicity
    change the permissions of inode 257, which results in # updating its inode item and therefore change (COW)
    only leaf 1. $ chmod 700 /mnt/testdir # Now fsync directory inode 257. # # Since only the first leaf was
    changed/COWed, we log the inode item of # inode 257 and only the dentries found in the first leaf, all
    have a # key type of BTRFS_DIR_ITEM_KEY, and no keys of type # BTRFS_DIR_INDEX_KEY, because they sort
    after the former type and none # exist in the first leaf. # # We also log 3 items that represent ranges
    for dir items and dir # indexes for which the log is authoritative: # # 1) a key of type
    BTRFS_DIR_LOG_ITEM_KEY, which indicates the log is # authoritative for all BTRFS_DIR_ITEM_KEY keys that
    have an offset # in the range [0, 2285968570] (the offset here is th ---truncated--- (CVE-2021-47072)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2021-47072");
  script_set_attribute(attribute:"solution", value:
"There is no known solution at this time.");
  script_set_attribute(attribute:"agent", value:"unix");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss3_score_source", value:"CVE-2021-47072");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
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  script_set_attribute(attribute:"vuln_publication_date", value:"2024/03/01");
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  script_copyright(english:"This script is Copyright (C) 2025 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info2.nasl", "set_linux_os_id.nasl");
  script_require_keys("Host/cpu", "Host/local_checks_enabled", "global_settings/vendor_unpatched", "Host/OS/identifier");
  script_require_ports("Host/OS/Ubuntu Linux-16.04", "Host/OS/Ubuntu Linux-18.04", "Host/OS/Ubuntu Linux-20.04", "Host/OS/Ubuntu Linux-22.04");

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if (!get_kb_item("global_settings/vendor_unpatched")) exit(0, "Unpatched Vulnerabilities Detection not active.");
if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (empty_or_null(get_one_kb_item("Host/Debian/dpkg-l"))) audit(AUDIT_PACKAGE_LIST_MISSING);

include('linux_unpatched.inc');

var distro_constraints_array = {
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "linux-hwe-edge"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "linux-aws-5.0"},
          {"reference": "linux-aws-5.3"},
          {"reference": "linux-azure-5.3"},
          {"reference": "linux-azure-cloud-tools-4.15.0"},
          {"reference": "linux-azure-edge"},
          {"reference": "linux-azure-headers-4.15.0"},
          {"reference": "linux-azure-tools-4.15.0"},
          {"reference": "linux-cloud-tools-4.15.0"},
          {"reference": "linux-gcp-5.3"},
          {"reference": "linux-gcp-headers-4.15.0"},
          {"reference": "linux-gcp-tools-4.15.0"},
          {"reference": "linux-gke-4.15"},
          {"reference": "linux-gke-5.4"},
          {"reference": "linux-gkeop-5.4"},
          {"reference": "linux-headers-4.15.0"},
          {"reference": "linux-hwe"},
          {"reference": "linux-hwe-edge"},
          {"reference": "linux-image-4.15.0"},
          {"reference": "linux-image-unsigned-4.15.0"},
          {"reference": "linux-modules-4.15.0"},
          {"reference": "linux-modules-extra-4.15.0"},
          {"reference": "linux-oem-headers-4.15.0"},
          {"reference": "linux-oem-tools-4.15.0"},
          {"reference": "linux-oracle-5.0"},
          {"reference": "linux-oracle-5.3"},
          {"reference": "linux-tools-4.15.0"},
          {"reference": "linux-udebs-azure"},
          {"reference": "linux-udebs-oem"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "linux-aws-5.11"},
          {"reference": "linux-aws-5.13"},
          {"reference": "linux-aws-5.8"},
          {"reference": "linux-azure-5.11"},
          {"reference": "linux-azure-5.13"},
          {"reference": "linux-azure-5.8"},
          {"reference": "linux-azure-fde"},
          {"reference": "linux-buildinfo-5.4.0"},
          {"reference": "linux-buildinfo-5.6.0"},
          {"reference": "linux-cloud-tools-5.4.0"},
          {"reference": "linux-cloud-tools-5.6.0"},
          {"reference": "linux-gcp-5.11"},
          {"reference": "linux-gcp-5.13"},
          {"reference": "linux-gcp-5.8"},
          {"reference": "linux-gke"},
          {"reference": "linux-gke-5.15"},
          {"reference": "linux-headers-5.4.0"},
          {"reference": "linux-headers-5.6.0"},
          {"reference": "linux-hwe-5.11"},
          {"reference": "linux-hwe-5.13"},
          {"reference": "linux-hwe-5.8"},
          {"reference": "linux-image-5.4.0"},
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          {"reference": "linux-libc-dev"},
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          {"reference": "linux-oem-5.6-headers-5.6.0"},
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          {"reference": "linux-oem-5.6-tools-common"},
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          {"reference": "linux-tools-5.4.0"},
          {"reference": "linux-tools-5.6.0"},
          {"reference": "linux-udebs-generic"},
          {"reference": "linux-udebs-oem"}
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      }
    ]
  },
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    "package_manager": "dpkg-l",
    "constraints": [
      {
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          {"reference": "linux-azure-5.19"},
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          {"reference": "linux-azure-fde-6.2"},
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          {"reference": "linux-image-5.15.0"},
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          {"reference": "linux-lowlatency-hwe-6.2"},
          {"reference": "linux-modules-5.15.0"},
          {"reference": "linux-modules-5.17.0"},
          {"reference": "linux-modules-extra-5.15.0"},
          {"reference": "linux-modules-extra-5.17.0"},
          {"reference": "linux-nvidia-6.2"},
          {"reference": "linux-oem-5.17-headers-5.17.0"},
          {"reference": "linux-oem-5.17-tools-5.17.0"},
          {"reference": "linux-oem-5.17-tools-host"},
          {"reference": "linux-oem-6.0"},
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};

var distro_constraints_values = linux_unpatched::get_distro_constraints(distro_constraints_arr:distro_constraints_array);
if (empty_or_null(distro_constraints_values)) audit(AUDIT_HOST_NOT, 'affected');
var report = linux_unpatched::check_unpatched_constraints(distro_constraints_values:distro_constraints_values);

if (!empty_or_null(report))
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_WARNING,
      extra      : report
  );
  exit(0);
}
else
{
  audit(AUDIT_HOST_NOT, 'affected');
}