Unity Linux 20.1050a Security Update: kernel (UTSA-2026-100722)

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

include('compat.inc');

if (description)
{
  script_id(336169);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/17");

  script_cve_id("CVE-2026-43439");

  script_name(english:"Unity Linux 20.1050a Security Update: kernel (UTSA-2026-100722)");

  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-2026-100722 advisory.

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

    cgroup: fix race between task migration and iteration

    When a task is migrated out of a css_set, cgroup_migrate_add_task()
    first moves it from cset->tasks to cset->mg_tasks via:

        list_move_tail(&task->cg_list, &cset->mg_tasks);

    If a css_task_iter currently has it->task_pos pointing to this task,
    css_set_move_task() calls css_task_iter_skip() to keep the iterator
    valid. However, since the task has already been moved to ->mg_tasks,
    the iterator is advanced relative to the mg_tasks list instead of the
    original tasks list. As a result, remaining tasks on cset->tasks, as
    well as tasks queued on cset->mg_tasks, can be skipped by iteration.

    Fix this by calling css_set_skip_task_iters() before unlinking
    task->cg_list from cset->tasks. This advances all active iterators to
    the next task on cset->tasks, so iteration continues correctly even
    when a task is concurrently being migrated.

    This race is hard to hit in practice without instrumentation, but it
    can be reproduced by artificially slowing down cgroup_procs_show().
    For example, on an Android device a temporary
    /sys/kernel/cgroup/cgroup_test knob can be added to inject a delay
    into cgroup_procs_show(), and then:

      1) Spawn three long-running tasks (PIDs 101, 102, 103).
      2) Create a test cgroup and move the tasks into it.
      3) Enable a large delay via /sys/kernel/cgroup/cgroup_test.
      4) In one shell, read cgroup.procs from the test cgroup.
      5) Within the delay window, in another shell migrate PID 102 by
         writing it to a different cgroup.procs file.

    Under this setup, cgroup.procs can intermittently show only PID 101
    while skipping PID 103. Once the migration completes, reading the
    file again shows all tasks as expected.

    Note that this change does not allow removing the existing
    css_set_skip_task_iters() call in css_set_move_task(). The new call
    in cgroup_migrate_add_task() only handles iterators that are racing
    with migration while the task is still on cset->tasks. Iterators may
    also start after the task has been moved to cset->mg_tasks. If we
    dropped css_set_skip_task_iters() from css_set_move_task(), such
    iterators could keep task_pos pointing to a migrating task, causing
    css_task_iter_advance() to malfunction on the destination css_set,
    up to and including crashes or infinite loops.

    The race window between migration and iteration is very small, and
    css_task_iter is not on a hot path. In the worst case, when an
    iterator is positioned on the first thread of the migrating process,
    cgroup_migrate_add_task() may have to skip multiple tasks via
    css_set_skip_task_iters(). However, this only happens when migration
    and iteration actually race, so the performance impact is negligible
    compared to the correctness fix provided here.

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-2026-100722
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?0144b241");
  # https://lore.kernel.org/linux-cve-announce/2026050853-CVE-2026-43439-131e@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?43d82d27");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2026-43439");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:H/Au:S/C:N/I:N/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:H/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:"cvss_score_source", value:"CVE-2026-43439");

  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:"2026/05/08");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/08/13");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/17");

  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_NOTE,
      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');
}