Unity Linux 20.1050a Security Update: kernel (UTSA-2026-006986)

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

include('compat.inc');

if (description)
{
  script_id(308290);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/04/21");

  script_cve_id("CVE-2025-39703");

  script_name(english:"Unity Linux 20.1050a Security Update: kernel (UTSA-2026-006986)");

  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-2026-006986 advisory.

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

    net, hsr: reject HSR frame if skb can't hold tag

    Receiving HSR frame with insufficient space to hold HSR tag in the skb
    can result in a crash (kernel BUG):

    [   45.390915] skbuff: skb_under_panic: text:ffffffff86f32cac len:26 put:14 head:ffff888042418000
    data:ffff888042417ff4 tail:0xe end:0x180 dev:bridge_slave_1
    [   45.392559] ------------[ cut here ]------------
    [   45.392912] kernel BUG at net/core/skbuff.c:211!
    [   45.393276] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI
    [   45.393809] CPU: 1 UID: 0 PID: 2496 Comm: reproducer Not tainted 6.15.0 #12 PREEMPT(undef)
    [   45.394433] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
    rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
    [   45.395273] RIP: 0010:skb_panic+0x15b/0x1d0

    <snip registers, remove unreliable trace>

    [   45.402911] Call Trace:
    [   45.403105]  <IRQ>
    [   45.404470]  skb_push+0xcd/0xf0
    [   45.404726]  br_dev_queue_push_xmit+0x7c/0x6c0
    [   45.406513]  br_forward_finish+0x128/0x260
    [   45.408483]  __br_forward+0x42d/0x590
    [   45.409464]  maybe_deliver+0x2eb/0x420
    [   45.409763]  br_flood+0x174/0x4a0
    [   45.410030]  br_handle_frame_finish+0xc7c/0x1bc0
    [   45.411618]  br_handle_frame+0xac3/0x1230
    [   45.413674]  __netif_receive_skb_core.constprop.0+0x808/0x3df0
    [   45.422966]  __netif_receive_skb_one_core+0xb4/0x1f0
    [   45.424478]  __netif_receive_skb+0x22/0x170
    [   45.424806]  process_backlog+0x242/0x6d0
    [   45.425116]  __napi_poll+0xbb/0x630
    [   45.425394]  net_rx_action+0x4d1/0xcc0
    [   45.427613]  handle_softirqs+0x1a4/0x580
    [   45.427926]  do_softirq+0x74/0x90
    [   45.428196]  </IRQ>

    This issue was found by syzkaller.

    The panic happens in br_dev_queue_push_xmit() once it receives a
    corrupted skb with ETH header already pushed in linear data. When it
    attempts the skb_push() call, there's not enough headroom and
    skb_push() panics.

    The corrupted skb is put on the queue by HSR layer, which makes a
    sequence of unintended transformations when it receives a specific
    corrupted HSR frame (with incomplete TAG).

    Fix it by dropping and consuming frames that are not long enough to
    contain both ethernet and hsr headers.

    Alternative fix would be to check for enough headroom before skb_push()
    in br_dev_queue_push_xmit().

    In the reproducer, this is injected via AF_PACKET, but I don't easily
    see why it couldn't be sent over the wire from adjacent network.

    Further Details:

    In the reproducer, the following network interface chain is set up:

    
    
     veth0_to_hsr     hsr_slave0    
    
       
                                               
                                               hsr0 
                                                  
    
                   
     veth1_to_hsr     hsr_slave1                        
    
                     bridge 
                                                                   
                                                           
                                                           
                                                  
                                              ...  
                                            

    To trigger the events leading up to crash, reproducer sends a corrupted
    HSR fr
    ---truncated---

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-2026-006986
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?55dadf4d");
  # https://lore.kernel.org/linux-cve-announce/2025090549-CVE-2025-39703-b03b@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?c543644f");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2025-39703");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/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: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:"cvss_score_source", value:"CVE-2025-39703");

  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:"2025/09/04");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/04/08");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/04/21");

  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:"^20.1050a([^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-5.10.0-27.5', 'sp':'1050a', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-27.5', 'sp':'1050a', 'cpu':'amd64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-27.5', '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');
}