Unity Linux 20.1050a Security Update: kernel (UTSA-2026-098904)

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

include('compat.inc');

if (description)
{
  script_id(340347);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/26");

  script_cve_id("CVE-2026-64456");

  script_name(english:"Unity Linux 20.1050a Security Update: kernel (UTSA-2026-098904)");

  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-2026-098904 advisory.

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

    hwrng: virtio: clamp device-reported used.len at copy_data()

    random_recv_done() stores the device-reported used.len directly into
    vi->data_avail.  copy_data() then indexes vi->data[] using
    vi->data_idx (advanced by previous copy_data() calls) and issues a
    memcpy() without re-validating either value against the posted
    buffer size sizeof(vi->data) (SMP_CACHE_BYTES bytes, typically 32
    or 64).

    A malicious or buggy virtio-rng backend can set used.len beyond
    sizeof(vi->data), steering the memcpy() past the end of the inline
    array into adjacent kmalloc-1k slab bytes.  hwrng_fillfn() mixes
    those bytes into the guest RNG, and guest root can also observe
    them directly via /dev/hwrng.

    Concrete impact is inside the guest:

     - Memory-safety / hardening: any virtio-rng backend that
       over-reports used.len causes the driver to read past vi->data
       into unrelated slab contents.  hwrng_fillfn() is a kernel thread
       that runs as soon as the device is probed; no guest userspace
       interaction is required to first-trigger the OOB.

     - Cross-boundary leak (confidential-compute threat model): a
       malicious hypervisor cooperating with a malicious or compromised
       guest root userspace can use /dev/hwrng as a leak channel for
       guest-kernel heap data.  The host sets a large used.len, guest
       root reads /dev/hwrng, and the returned bytes contain guest
       kernel slab contents that were adjacent to vi->data.  In
       practice, confidential-compute guests (SEV-SNP, TDX) usually
       disable virtio-rng entirely, so this path is narrow, but the
       fix is still worth carrying because the underlying
       memory-safety bug contaminates the guest RNG on any host.

    KASAN confirms the OOB on a 7.1-rc4 guest whose virtio-rng backend
    has been patched to report used.len = 0x10000:

      BUG: KASAN: slab-out-of-bounds in virtio_read+0x394/0x5d0
      Read of size 64 at addr ffff88800ae0ba20 by task hwrng/52
      Call Trace:
       __asan_memcpy+0x23/0x60
       virtio_read+0x394/0x5d0
       hwrng_fillfn+0xb2/0x470
       kthread+0x2cc/0x3a0
      Allocated by task 1:
       probe_common+0xa5/0x660
       virtio_dev_probe+0x549/0xbc0
      The buggy address belongs to the object at ffff88800ae0b800
       which belongs to the cache kmalloc-1k of size 1024
      The buggy address is located 0 bytes to the right of
       allocated 544-byte region [ffff88800ae0b800, ffff88800ae0ba20)

    Same class of bug as commit c04db81cd028 (net/9p: Fix buffer
    overflow in USB transport layer), which hardened
    usb9pfs_rx_complete() against unchecked device-reported length in
    the USB 9p transport.

    With the clamp at point of use and array_index_nospec() in place,
    the same harness boots cleanly: copy_data() returns zero for the
    bogus report, the device-supplied bytes after data_idx are
    discarded, and the driver issues a fresh request.

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-2026-098904
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?0bbac3db");
  # https://lore.kernel.org/linux-cve-announce/2026072542-CVE-2026-64456-ccb5@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?4d849bb9");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2026-64456");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:C/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:N/UI:N/S:U/C:H/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-2026-64456");

  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:"2026/07/23");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/08/10");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/26");

  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 && 'loongarch64' >!< cpu && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'UOS Server', cpu);


var constraints = [
  {
    'release': '20',
    'sp': '1050a',
    'pkgs': [
      {'reference':'kernel-4.19.0-91.82.132.24.uelc20', 'sp':'1050a', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-4.19.0-91.82.132.24.uelc20', 'sp':'1050a', 'cpu':'amd64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-4.19.0-91.82.132.24.uelc20', 'sp':'1050a', 'cpu':'loongarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'kernel-4.19.0-91.82.132.24.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');
}