Unity Linux 20.1050a Security Update: kernel (UTSA-2026-104554)

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

include('compat.inc');

if (description)
{
  script_id(339556);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/26");

  script_cve_id("CVE-2026-72108");

  script_name(english:"Unity Linux 20.1050a Security Update: kernel (UTSA-2026-104554)");

  script_set_attribute(attribute:"synopsis", value:
"The Unity Linux host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the
UTSA-2026-104554 advisory.

    In the Linux kernel, the following vulnerability has been resolved:

    dm thin metadata: fix metadata snapshot consistency on commit failure

    __reserve_metadata_snap() and __release_metadata_snap() modify the
    superblock's held_root directly in the block_manager's buffer. If the
    subsequent metadata commit fails, the held_root gets flushed to disk
    through the abort_transaction path, resulting in inconsistent metadata.

    Reproducer 1: __reserve_metadata_snap()

    1. Create a 2 MiB metadata device and make the region after the 14th
       block inaccessible, to trigger metadata commit failure in the
       subsequent reserve_metadata_snap operation. The 14th block will be
       the shadow destination for the index block.

    dmsetup create tmeta --table 0 112 linear /dev/sdc 0
    112 3984 error

    2. Create a 16 MiB thin-pool

    dmsetup create tdata --table 0 32768 zero
    dd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1
    dmsetup create tpool --table 0 32768 thin-pool /dev/mapper/tmeta
    /dev/mapper/tdata 128 0 1 skip_block_zeroing

    3. Take a metadata snapshot to trigger metadata commit failure and
       transaction abort. However, the held_root is written to disk,
       breaking metadata consistency.

    dmsetup message tpool 0 reserve_metadata_snap

    thin_check v1.2.2 result:

    Bad reference count for metadata block 6.  Expected 2, but space map contains 1.
    Bad reference count for metadata block 7.  Expected 2, but space map contains 1.
    Bad reference count for metadata block 13.  Expected 1, but space map contains 0.

    Reproducer 2: __release_metadata_snap()

    1. Create a 2 MiB metadata device and make the region after the 16th
       block inaccessible, to trigger metadata commit failure in the
       subsequent release_metadata_snap operation. The 16th block will be
       the shadow destination for the index block.

    dmsetup create tmeta --table 0 128 linear /dev/sdc 0
    128 3968 error

    2. Create a 16 MiB thin-pool

    dmsetup create tdata --table 0 32768 zero
    dd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1
    dmsetup create tpool --table 0 32768 thin-pool /dev/mapper/tmeta
    /dev/mapper/tdata 128 0 1 skip_block_zeroing

    3. Reserve then release the metadata snapshot, to trigger metadata
       commit failure and transaction abort. The held_root gets removed
       from the on-disk superblock, causing inconsistent metadata.

    dmsetup message tpool 0 reserve_metadata_snap
    dmsetup message tpool 0 release_metadata_snap

    thin_check v1.2.2 result:

    Bad reference count for metadata block 6.  Expected 1, but space map contains 2.
    Bad reference count for metadata block 7.  Expected 1, but space map contains 2.
    1 metadata blocks have leaked.

    Fix by deferring the held_root update to commit time.

    Additionally, move the existing-snapshot check in __reserve_metadata_snap
    before the shadow operation to avoid unnecessary work. In
    __release_metadata_snap, clear pmd->held_root before btree deletion so
    partial failure leaks blocks rather than leaving a stale reference, and
    unlock the snapshot block before decrementing its refcount.

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  # https://src.uniontech.com/#/security_advisory_detail?utsa_id=UTSA-2026-104554
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?186d4ab2");
  # https://lore.kernel.org/linux-cve-announce/2026081526-CVE-2026-72108-5b5e@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?a2ad6463");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2026-72108");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/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:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-72108");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/08/11");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/08/25");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/26");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

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

  script_copyright(english:"This script is Copyright (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info2.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/UOS-Server/release", "Host/UOS-Server/rpm-list", "Host/cpu");

  exit(0);
}
include('rpm2.inc');

if (!get_kb_item('Host/local_checks_enabled')) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_product = get_kb_item('installed_os/local/SSH/0/product');
if (isnull(os_product) || 'UOS Server' >!< os_product) audit(AUDIT_OS_NOT, 'UOS Server');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'UOS Server');
if (! preg(pattern:"^(20.1050a)([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'UOS Server 20.1050a', 'UOS Server ' + os_version);

if (!get_kb_item('Host/UOS-Server/rpm-list')) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('aarch64' >!< cpu && 'amd64' >!< cpu && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'UOS Server', cpu);


var constraints = [
  {
    'release': '20',
    'sp': '1050a',
    'pkgs': [
      {'reference':'kernel-5.10.0-27.18.uelc20', 'sp':'1050a', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-27.18.uelc20', 'sp':'1050a', 'cpu':'amd64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-27.18.uelc20', 'sp':'1050a', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE}
    ]
  }
];

var os_release = get_one_kb_item('installed_os/local/SSH/0/release');
var os_sp = get_one_kb_item('Host/*/minor_release');

var flag = 0;
var reference;
var sp;
var _cpu;
var el_string;
var rpm_spec_vers_cmp;
var epoch;
var allowmaj;
var exists_check;
var cves;
foreach var constraint ( constraints ) {
  # Check that the target release is equal to the affected release
  if (!empty_or_null(constraint['release'])){
    if (constraint['release'] != os_release) continue;
  }
  if (!empty_or_null(constraint['sp'])){
    if (constraint['sp'] != os_sp) continue;
  }
  foreach var pkg ( constraint['pkgs'] ) {
    reference = NULL;
    sp = NULL;
    _cpu = NULL;
    el_string = NULL;
    rpm_spec_vers_cmp = NULL;
    epoch = NULL;
    allowmaj = NULL;
    exists_check = NULL;
    cves = NULL;
    if (!empty_or_null(pkg['reference'])) reference = pkg['reference'];
    if (!empty_or_null(pkg['sp'])) sp = pkg['sp'];
    if (!empty_or_null(pkg['cpu'])) _cpu = pkg['cpu'];
    if (!empty_or_null(pkg['el_string'])) el_string = pkg['el_string'];
    if (!empty_or_null(pkg['rpm_spec_vers_cmp'])) rpm_spec_vers_cmp = pkg['rpm_spec_vers_cmp'];
    if (!empty_or_null(pkg['epoch'])) epoch = pkg['epoch'];
    if (!empty_or_null(pkg['allowmaj'])) allowmaj = pkg['allowmaj'];
    if (!empty_or_null(pkg['exists_check'])) exists_check = pkg['exists_check'];
    if (!empty_or_null(pkg['cves'])) cves = pkg['cves'];
    if (reference &&
        ## (no known rpm to check OR known rpm_exists)
        (!exists_check || rpm_exists(rpm:exists_check)) &&
        rpm_check(sp:sp, cpu:_cpu, reference:reference, epoch:epoch, el_string:el_string, rpm_spec_vers_cmp:rpm_spec_vers_cmp, allowmaj:allowmaj, cves:cves)) flag++;
  }
}


if (flag)
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_WARNING,
      extra      : rpm_report_get()
  );
  exit(0);
}
else
{
  var tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'kernel');
}