Alibaba Cloud Linux 3 : 0314: unbound (ALINUX3-SA-2026:0314)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The package checks in this plugin were extracted from
# Alibaba Cloud Linux Security Advisory ALINUX3-SA-2026:0314.
##

include('compat.inc');

if (description)
{
  script_id(367785);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/20");

  script_cve_id(
    "CVE-2026-50252",
    "CVE-2026-81634",
    "CVE-2026-81642",
    "CVE-2026-82717"
  );

  script_name(english:"Alibaba Cloud Linux 3 : 0314: unbound (ALINUX3-SA-2026:0314)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Alibaba Cloud Linux host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The remote Alibaba Cloud Linux 3 host has packages installed that are affected by multiple vulnerabilities as referenced
in the ALINUX3-SA-2026:0314 advisory.

    Package updates are available for Alibaba Cloud Linux 3 that fix the following vulnerabilities:

    CVE-2026-50252:
    In NLnet Labs Unbound 1.4.22 up to and including 1.25.1, UDP source port is randomized and intended to
    serve as a secret value that increases the entropy of DNS transactions. When resolver load balancing
    policies depend on the source port while their outcome is revealed this secrecy is undermined. The
    vulnerability arises when the load balancing policy is consistent with respect to the incoming source UDP
    port and IP address while heavily depending on the incoming source UDP port as a randomization source.
    When the SO_REUSEPORT configuration option is enabled ('so-reuseport: yes') in Unbound (by default), it
    meets these conditions, making it vulnerable for DNS cache poisoning attacks. Upon startup, Unbound
    randomly partitions the available UDP source port space into disjoint subsets of (almost) equal size,
    assigning each subset to a specific worker thread. When an incoming DNS query is received, the kernels
    SO_REUSEPORT load balancing mechanism deterministically assigns the query to a socket associated with a
    particular thread. All outgoing DNS queries generated during the resolution of that request use source
    ports selected exclusively from the port subset assigned to the corresponding thread. Since these port
    subsets are disjoint across threads, the source port observed in a resolvers outgoing query to an
    authoritative name server serves as a reliable indicator of the worker thread that processed the original
    client query. A malicious actor can acquire the mapping between incoming UDP source ports (for a given
    fixed source IP address) and Unbound worker threads and leverage it to conduct DNS cache poisoning attacks
    by effectively lowering the random port population per thread.

    CVE-2026-81634:
    In NLnet Labs Unbound up to and including 1.26.0, a 255 length query name with a large TCP response can
    lead to a heap buffer overflow during the RRSet canonicalisation routine. This is caused by missing to add
    the first owner name into the buffer length check. A malicious actor operating a malicious name server or
    tampering with an incoming response to Unbound (canonicalisation happens before DNSSEC validation), can
    trigger the vulnerability.

    CVE-2026-81642:
    In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in the DNSSEC validator that
    enables denial of service and possible remote code execution as a result of digesting DNSKEYs. A DNSKEY
    with an owner compression pointer to its own RDATA can overflow the digest buffer. Remote code execution
    is possible through attacker controlled data. An adversary can exploit the vulnerability by controlling a
    malicious zone and querying a vulnerable Unbound.

    CVE-2026-82717:
    In NLnet Labs Unbound up to and including 1.26.0, a vulnerability was found in that can progressively
    corrupt heap memory and under certain systems and compilation options could lead to remote code execution.
    The vulnerability starts when CNAME synthesis during an upstream response needs to enforce(rewrite) a max
    TTL value in the packet buffer. Coupled with a compression pointer that points to the overwritten value
    and invalidates the domain name, it leads to an error path that does not properly move the buffer position
    and allows for the heap buffer overflow. Since this is heavily reliant on heap memory layout, results are
    memory corruption that eventually leads to a crash and under specific systems and compilation options
    remote code execution.

Tenable has extracted the preceding description block directly from the Alibaba Cloud Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"http://mirrors.aliyun.com/alinux/3/cve/alinux3-sa-20260314.xml");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages.");
  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:"cvss4_vector", value:"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:U");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-82717");
  script_set_attribute(attribute:"cvss4_score_source", value:"CVE-2026-81642");

  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:"2026/07/22");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/10/19");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/20");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:python3-unbound");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:unbound");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:unbound-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:unbound-libs");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:alibabacloud:alibaba_cloud_linux_3");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Alibaba Cloud 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/Alibaba/release", "Host/Alibaba/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) || 'Alibaba Cloud Linux' >!< os_product) audit(AUDIT_OS_NOT, 'Alibaba Cloud Linux');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'Alibaba Cloud Linux');
if (! preg(pattern:"^3([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'Alibaba Cloud Linux 3.x', 'Alibaba Cloud Linux ' + os_version);

if (!get_kb_item('Host/Alibaba/rpm-list')) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('aarch64' >!< cpu && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Alibaba Cloud Linux', cpu);

var constraints = [
  {
    'release': '3',
    'pkgs': [
      {'reference':'python3-unbound-1.16.2-9.0.5.al8', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
      {'reference':'python3-unbound-1.16.2-9.0.5.al8', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
      {'reference':'unbound-1.16.2-9.0.5.al8', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
      {'reference':'unbound-1.16.2-9.0.5.al8', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
      {'reference':'unbound-devel-1.16.2-9.0.5.al8', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
      {'reference':'unbound-devel-1.16.2-9.0.5.al8', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
      {'reference':'unbound-libs-1.16.2-9.0.5.al8', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'},
      {'reference':'unbound-libs-1.16.2-9.0.5.al8', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE, 'epoch':'0'}
    ]
  }
];

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, 'python3-unbound / unbound / unbound-devel / unbound-libs');
}