Unity Linux 20.1050e Security Update: kernel (UTSA-2026-102020)

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

include('compat.inc');

if (description)
{
  script_id(338584);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/21");

  script_cve_id("CVE-2026-46099");

  script_name(english:"Unity Linux 20.1050e Security Update: kernel (UTSA-2026-102020)");

  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-2026-102020 advisory.

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

    net: ipv6: fix NOREF dst use in seg6 and rpl lwtunnels

    seg6_input_core() and rpl_input() call ip6_route_input() which sets a
    NOREF dst on the skb, then pass it to dst_cache_set_ip6() invoking
    dst_hold() unconditionally.
    On PREEMPT_RT, ksoftirqd is preemptible and a higher-priority task can
    release the underlying pcpu_rt between the lookup and the caching
    through a concurrent FIB lookup on a shared nexthop.
    Simplified race sequence:

      ksoftirqd/X                       higher-prio task (same CPU X)
      -----------                       --------------------------------
      seg6_input_core(,skb)/rpl_input(skb)
        dst_cache_get()
          -> miss
        ip6_route_input(skb)
          -> ip6_pol_route(,skb,flags)
             [RT6_LOOKUP_F_DST_NOREF in flags]
            -> FIB lookup resolves fib6_nh
               [nhid=N route]
            -> rt6_make_pcpu_route()
               [creates pcpu_rt, refcount=1]
                 pcpu_rt->sernum = fib6_sernum
                 [fib6_sernum=W]
               -> cmpxchg(fib6_nh.rt6i_pcpu,
                          NULL, pcpu_rt)
                  [slot was empty, store succeeds]
          -> skb_dst_set_noref(skb, dst)
             [dst is pcpu_rt, refcount still 1]

                                        rt_genid_bump_ipv6()
                                          -> bumps fib6_sernum
                                             [fib6_sernum from W to Z]
                                        ip6_route_output()
                                          -> ip6_pol_route()
                                            -> FIB lookup resolves fib6_nh
                                               [nhid=N]
                                            -> rt6_get_pcpu_route()
                                                 pcpu_rt->sernum != fib6_sernum
                                                 [W <> Z, stale]
                                              -> prev = xchg(rt6i_pcpu, NULL)
                                              -> dst_release(prev)
                                                 [prev is pcpu_rt,
                                                  refcount 1->0, dead]

        dst = skb_dst(skb)
        [dst is the dead pcpu_rt]
        dst_cache_set_ip6(dst)
          -> dst_hold() on dead dst
          -> WARN / use-after-free

    For the race to occur, ksoftirqd must be preemptible (PREEMPT_RT without
    PREEMPT_RT_NEEDS_BH_LOCK) and a concurrent task must be able to release
    the pcpu_rt. Shared nexthop objects provide such a path, as two routes
    pointing to the same nhid share the same fib6_nh and its rt6i_pcpu
    entry.

    Fix seg6_input_core() and rpl_input() by calling skb_dst_force() after
    ip6_route_input() to force the NOREF dst into a refcounted one before
    caching.
    The output path is not affected as ip6_route_output() already returns a
    refcounted dst.

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-2026-102020
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?d2f78dd2");
  # https://lore.kernel.org/linux-cve-announce/2026052704-CVE-2026-46099-2a55@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?7bd19d2e");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2026-46099");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:H/Au:N/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:L/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-2026-46099");

  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:"2026/05/27");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/08/17");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/21");

  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:"^(20.1050e)([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'UOS Server 20.1050e', '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': '1050e',
    'pkgs': [
      {'reference':'kernel-4.19.90-2211.5.0.0178.67.uel20', 'sp':'1050e', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-4.19.90-2211.5.0.0178.67.uel20', 'sp':'1050e', 'cpu':'amd64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-4.19.90-2211.5.0.0178.67.uel20', 'sp':'1050e', '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_HOLE,
      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');
}