Unity Linux 20.1050e Security Update: kernel (UTSA-2026-102004)

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

include('compat.inc');

if (description)
{
  script_id(337272);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/18");

  script_cve_id("CVE-2026-46113");

  script_name(english:"Unity Linux 20.1050e Security Update: kernel (UTSA-2026-102004)");

  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-2026-102004 advisory.

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

    KVM: x86: Fix shadow paging use-after-free due to unexpected GFN

    The shadow MMU computes GFNs for direct shadow pages using sp->gfn plus
    the SPTE index. This assumption breaks for shadow paging if the guest
    page tables are modified between VM entries (similar to commit
    aad885e77496, KVM: x86/mmu: Drop/zap existing present SPTE even
    when creating an MMIO SPTE, 2026-03-27).  The flow is as follows:

    - a PDE is installed for a 2MB mapping, and a page in that area is
      accessed.  KVM creates a kvm_mmu_page consisting of 512 4KB pages;
      the kvm_mmu_page is marked by FNAME(fetch) as direct-mapped because
      the guest's mapping is a huge page (and thus contiguous).

    - the PDE mapping is changed from outside the guest.

    - the guest accesses another page in the same 2MB area.  KVM installs
      a new leaf SPTE and rmap entry; the SPTE uses the correct GFN
      (i.e. based on the new mapping, as changed in the previous step) but
      that GFN is outside of the [sp->gfn, sp->gfn + 511] range; therefore
      the rmap entry cannot be found and removed when the kvm_mmu_page
      is zapped.

    - the memslot that covers the first 2MB mapping is deleted, and the
      kvm_mmu_page for the now-invalid GPA is zapped.  However, rmap_remove()
      only looks at the [sp->gfn, sp->gfn + 511] range established in step 1,
      and fails to find the rmap entry that was recorded by step 3.

    - any operation that causes an rmap walk for the same page accessed
      by step 3 then walks a stale rmap and dereferences a freed kvm_mmu_page.
      This includes dirty logging or MMU notifier invalidations (e.g., from
      MADV_DONTNEED).

    The underlying issue is that KVM's walking of shadow PTEs assumes that
    if a SPTE is present when KVM wants to install a non-leaf SPTE, then the
    existing kvm_mmu_page must be for the correct gfn.  Because the only way
    for the gfn to be wrong is if KVM messed up and failed to zap a SPTE...
    which shouldn't happen, but *actually* only happens in response to a
    guest write.

    That bug dates back literally forever, as even the first version of KVM
    assumes that the GFN matches and walks into the wrong shadow page.
    However, that was only an imprecision until 2032a93d66fa (KVM: MMU:
    Don't allocate gfns page for direct mmu pages) came along.

    Fix it by checking for a target gfn mismatch and zapping the existing
    SPTE.  That way the old SP and rmap entries are gone, KVM installs
    the rmap in the right location, and everyone is happy.

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-2026-102004
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?231d11a8");
  # https://lore.kernel.org/linux-cve-announce/2026052813-CVE-2026-46113-f083@gregkh
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?24b8411e");
  script_set_attribute(attribute:"see_also", value:"https://nvd.nist.gov/vuln/detail/CVE-2026-46113");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:S/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:C/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-2026-46113");

  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:"2026/05/28");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/08/17");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/18");

  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_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');
}