Unity Linux 20.1050a Security Update: kernel (UTSA-2026-100720)

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

include('compat.inc');

if (description)
{
  script_id(336639);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/17");

  script_cve_id("CVE-2026-46319");

  script_name(english:"Unity Linux 20.1050a Security Update: kernel (UTSA-2026-100720)");

  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-2026-100720 advisory.

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

    net/sched: act_ct: Only release RCU read lock after ct_ft

    When looking up a flow table in act_ct in tcf_ct_flow_table_get(),
    rhashtable_lookup_fast() internally opens and closes an RCU read critical
    section before returning ct_ft.
    The tcf_ct_flow_table_cleanup_work() can complete before refcount_inc_not_zero()
    is invoked on the returned ct_ft resulting in a UAF on the already freed ct_ft
    object. This vulnerability can lead to privilege escalation.

    Analysis from [email protected]:
    When initializing act_ct, tcf_ct_init() is called, which internally triggers
    tcf_ct_flow_table_get().

    static int tcf_ct_flow_table_get(struct net *net, struct tcf_ct_params *params)

    {
                    struct zones_ht_key key = { .net = net, .zone = params->zone };
                    struct tcf_ct_flow_table *ct_ft;
                    int err = -ENOMEM;

                    mutex_lock(&zones_mutex);
                    ct_ft = rhashtable_lookup_fast(&zones_ht, &key, zones_params); // [1]
                    if (ct_ft && refcount_inc_not_zero(&ct_ft->ref)) // [2]
                                    goto out_unlock;
                    ...
    }

    static __always_inline void *rhashtable_lookup_fast(
                    struct rhashtable *ht, const void *key,
                    const struct rhashtable_params params)
    {
                    void *obj;

                    rcu_read_lock();
                    obj = rhashtable_lookup(ht, key, params);
                    rcu_read_unlock();

                    return obj;
    }

    At [1], rhashtable_lookup_fast() looks up and returns the corresponding ct_ft
    from zones_ht . The lookup is performed within an RCU read critical section
    through rcu_read_lock() / rcu_read_unlock(), which prevents the object from
    being freed. However, at the point of function return, rcu_read_unlock() has
    already been called, and there is nothing preventing ct_ft from being freed
    before reaching refcount_inc_not_zero(&ct_ft->ref) at [2]. This interval becomes
    the race window, during which ct_ft can be freed.

    Free Process:

    tcf_ct_flow_table_put() is executed through the path tcf_ct_cleanup() call_rcu()
    tcf_ct_params_free_rcu() tcf_ct_params_free() tcf_ct_flow_table_put().

    static void tcf_ct_flow_table_put(struct tcf_ct_flow_table *ct_ft)
    {
                    if (refcount_dec_and_test(&ct_ft->ref)) {
                                    rhashtable_remove_fast(&zones_ht, &ct_ft->node, zones_params);
                                    INIT_RCU_WORK(&ct_ft->rwork, tcf_ct_flow_table_cleanup_work); // [3]
                                    queue_rcu_work(act_ct_wq, &ct_ft->rwork);
                    }
    }

    At [3], tcf_ct_flow_table_cleanup_work() is scheduled as RCU work

    static void tcf_ct_flow_table_cleanup_work(struct work_struct *work)

    {
                    struct tcf_ct_flow_table *ct_ft;
                    struct flow_block *block;

                    ct_ft = container_of(to_rcu_work(work), struct tcf_ct_flow_table,
                                                                    rwork);
                    nf_flow_table_free(&ct_ft->nf_ft);
                    block = &ct_ft->nf_ft.flow_block;
                    down_write(&ct_ft->nf_ft.flow_block_lock);
                    WARN_ON(!list_empty(&block->cb_list));
                    up_write(&ct_ft->nf_ft.flow_block_lock);
                    kfree(ct_ft); // [4]

                    module_put(THIS_MODULE);
    }

    tcf_ct_flow_table_cleanup_work() frees ct_ft at [4]. When this function executes
    between [1] and [2], UAF occurs.

    This race condition has a very short race window, making it generally
    difficult to trigger. Therefore, to trigger the vulnerability an msleep(100) was
    inserted after[1]

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-2026-100720
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?1ed2a36d");
  # https://lore.kernel.org/linux-cve-announce/2026060925-CVE-2026-46319-ab3d@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?79fd5cc1");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2026-46319");
  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-2026-46319");

  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:"2026/06/09");
  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_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');
}