Unity Linux 20.1050e Security Update: kernel (UTSA-2026-006691)

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

include('compat.inc');

if (description)
{
  script_id(305553);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/04/08");

  script_cve_id("CVE-2023-53585");

  script_name(english:"Unity Linux 20.1050e Security Update: kernel (UTSA-2026-006691)");

  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-2026-006691 advisory.

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

    bpf: reject unhashed sockets in bpf_sk_assign

    The semantics for bpf_sk_assign are as follows:

        sk = some_lookup_func()
        bpf_sk_assign(skb, sk)
        bpf_sk_release(sk)

    That is, the sk is not consumed by bpf_sk_assign. The function
    therefore needs to make sure that sk lives long enough to be
    consumed from __inet_lookup_skb. The path through the stack for a
    TCPv4 packet is roughly:

      netif_receive_skb_core: takes RCU read lock
        __netif_receive_skb_core:
          sch_handle_ingress:
            tcf_classify:
              bpf_sk_assign()
          deliver_ptype_list_skb:
            deliver_skb:
              ip_packet_type->func == ip_rcv:
                ip_rcv_core:
                ip_rcv_finish_core:
                  dst_input:
                    ip_local_deliver:
                      ip_local_deliver_finish:
                        ip_protocol_deliver_rcu:
                          tcp_v4_rcv:
                            __inet_lookup_skb:
                              skb_steal_sock

    The existing helper takes advantage of the fact that everything
    happens in the same RCU critical section: for sockets with
    SOCK_RCU_FREE set bpf_sk_assign never takes a reference.
    skb_steal_sock then checks SOCK_RCU_FREE again and does sock_put
    if necessary.

    This approach assumes that SOCK_RCU_FREE is never set on a sk
    between bpf_sk_assign and skb_steal_sock, but this invariant is
    violated by unhashed UDP sockets. A new UDP socket is created
    in TCP_CLOSE state but without SOCK_RCU_FREE set. That flag is only
    added in udp_lib_get_port() which happens when a socket is bound.

    When bpf_sk_assign was added it wasn't possible to access unhashed
    UDP sockets from BPF, so this wasn't a problem. This changed
    in commit 0c48eefae712 (sock_map: Lift socket state restriction
    for datagram sockets), but the helper wasn't adjusted accordingly.
    The following sequence of events will therefore lead to a refcount
    leak:

    1. Add socket(AF_INET, SOCK_DGRAM) to a sockmap.
    2. Pull socket out of sockmap and bpf_sk_assign it. Since
       SOCK_RCU_FREE is not set we increment the refcount.
    3. bind() or connect() the socket, setting SOCK_RCU_FREE.
    4. skb_steal_sock will now set refcounted = false due to
       SOCK_RCU_FREE.
    5. tcp_v4_rcv() skips sock_put().

    Fix the problem by rejecting unhashed sockets in bpf_sk_assign().
    This matches the behaviour of __inet_lookup_skb which is ultimately
    the goal of bpf_sk_assign().

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-2026-006691
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?3c76baa6");
  # https://lore.kernel.org/linux-cve-announce/2025100425-CVE-2023-53585-b855@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?6723da51");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2023-53585");
  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-2023-53585");

  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:"2021/07/21");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/04/08");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/04/08");

  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-5.10.0-27.5', 'sp':'1050e', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-27.5', 'sp':'1050e', 'cpu':'amd64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-5.10.0-27.5', '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_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');
}