Unity Linux 20.1050a Security Update: kernel (UTSA-2026-100567)

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

include('compat.inc');

if (description)
{
  script_id(336528);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/17");

  script_cve_id("CVE-2026-63888");

  script_name(english:"Unity Linux 20.1050a Security Update: kernel (UTSA-2026-100567)");

  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-2026-100567 advisory.

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

    scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()

    Two latent bugs in the Text-phase handler, both present since the
    original LIO integration in commit e48354ce078c (iscsi-target: Add
    iSCSI fabric support for target v4.1):

    1) DataDigest CRC buffer overread (4 bytes past text_in).

       text_in is kzalloc()'d at ALIGN(payload_length, 4).  rx_size is then
       incremented by ISCSI_CRC_LEN to make room for the received DataDigest
       in the iovec, but the same (now-bumped) rx_size is passed as the
       buffer length to iscsit_crc_buf():

           if (conn->conn_ops->DataDigest) {
                   ...
                   rx_size += ISCSI_CRC_LEN;
           }
           ...
           if (conn->conn_ops->DataDigest) {
                   data_crc = iscsit_crc_buf(text_in, rx_size, 0, NULL);

       iscsit_crc_buf() walks rx_size bytes of text_in with crc32c(), so
       when DataDigest is negotiated it reads 4 bytes past the end of the
       text_in allocation.  KASAN reproduces this directly on the unpatched
       mainline tree as slab-out-of-bounds in crc32c() called from the Text
       PDU path.  The OOB bytes feed crc32c() and are then compared against
       the initiator-supplied checksum, so the value does not flow back to
       the attacker, but the kernel does read past the buffer on every Text
       PDU with DataDigest=CRC32C.

       Fix by passing the actual padded payload length
       (ALIGN(payload_length, 4)) that was used for the kzalloc().

    2) Stale cmd->text_in_ptr re-free (double-free) on ERL>0 bad DataDigest
       drop.

       On DataDigest mismatch with ErrorRecoveryLevel > 0 the handler
       silently drops the PDU and lets the initiator plug the CmdSN gap:

                   kfree(text_in);
                   return 0;

       cmd->text_in_ptr still points at the freed buffer.  The next Text
       Request on the same ITT re-enters iscsit_setup_text_cmd(), which
       unconditionally does

           kfree(cmd->text_in_ptr);
           cmd->text_in_ptr = NULL;

       freeing the same pointer a second time.  Session teardown via
       iscsit_release_cmd() has the same shape and hits the same double-free
       if the connection is dropped before a second Text Request arrives.

       On an unmodified mainline tree the bug-1 CRC overread fires first on
       the initial valid Text Request and perturbs the subsequent state, so
       #4 was isolated by building a kernel with only the bug-1 hunk of this
       patch applied plus temporary printk() observability around the three
       relevant kfree() sites.  The observability prints are not part of
       this patch.  On that build, a three-PDU Text Request sequence after
       login produces two back-to-back splats:

           BUG: KASAN: double-free in iscsit_setup_text_cmd+0x??
           BUG: KASAN: double-free in iscsit_release_cmd+0x??

       showing the same pointer freed in the ERL>0 drop path and again in
       iscsit_setup_text_cmd() (next Text Request on the same ITT) and once
       more in iscsit_release_cmd() (session teardown).  On distro kernels
       with CONFIG_SLAB_FREELIST_HARDENED=y (default) the double-free
       becomes a remote kernel BUG(); on non-hardened kernels it corrupts
       the slab freelist.

       Fix by clearing cmd->text_in_ptr after the kfree() in the ERL>0 drop
       path.  With both hunks applied #4 is directly observable on the stock
       tree without observability printks; fixing bug-1 alone would mask #4
       less, not more, so the hunks are submitted together.

    Both fixes are one-liners.  The Text PDU state machine is unchanged and
    the wire protocol is unaffected.

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-2026-100567
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?132e8d3c");
  # https://lore.kernel.org/linux-cve-announce/2026071940-CVE-2026-63888-a5d6@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?c0eaec98");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2026-63888");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/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:N/AC:L/PR:N/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-2026-63888");

  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:"2026/07/07");
  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_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');
}