CentOS Linux 7 [TuxCare] Security Update: unbound / unbound-devel / unbound-libs / unbound-python Multiple Vulnerabilities (CENTOS7:CLSA-2026:1791327169)

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

include('compat.inc');

if (description)
{
  script_id(364644);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/12");

  script_cve_id(
    "CVE-2026-81634",
    "CVE-2026-81642",
    "CVE-2026-82717",
    "CVE-2026-85501"
  );
  script_xref(name:"CLSA", value:"2026:1791327169");

  script_name(english:"CentOS Linux 7 [TuxCare] Security Update: unbound / unbound-devel / unbound-libs / unbound-python Multiple Vulnerabilities (CENTOS7:CLSA-2026:1791327169)");

  script_set_attribute(attribute:"synopsis", value:
"The CentOS Linux host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The CentOS Linux 7 host has packages installed that are affected by multiple vulnerabilities as referenced in the
TuxCare CENTOS7:CLSA-2026:1791327169 advisory.

  - 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-2026-81634)

  - 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-2026-81642)

  - 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. (CVE-2026-82717)

  - Novel vulnerabilities to launch algorithmic complexity attacks on DNSSEC have been researched under the
    term 'ReTrap'. These result in degradation of service when malicious zones are used to serve the
    algorithmic complexity vulnerabilities. NLnet Labs Unbound up to and including 1.26.0 is vulnerable to
    some of them. TagTrap, where the triple(Zone, Algo, KeyTag) matching mechanism introduces a significant
    attack vector when resolvers handle malicious responses containing numerous mismatched DNSKEY, RRSIG, and
    DS record. DelegationTrap, where constructing the chain-of-trust requires iterative validation of DNSKEY
    and DS records from the root zone downward. For deeply nested domains, this results in significant
    computational overhead. NsecTrap, where responses with excessive invalid NSEC records compel the resolver
    to validate each one. AdditionalTrap, where Unbound by default would try to DNSSEC validate the ADDITIONAL
    section as well. This can be exploited to waste validation resources by malicious users. (CVE-2026-85501)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version
number.");
  # https://security.tuxcare.com/csaf/v2/els_os/centos7els/advisories/2026/clsa-2026_1791327169.json
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?9f41bc00");
  script_set_attribute(attribute:"see_also", value:"https://cve.tuxcare.com/els/releases/CLSA-2026:1791327169");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages based on the guidance in TuxCare advisory CENTOS7:CLSA-2026:1791327169.");
  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:"vendor_severity", value:"Critical");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/09/16");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/10/06");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/12");

  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:"CentOS 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/OS/extended-third-party", "Host/local_checks_enabled", "Host/CentOS/release", "Host/CentOS/rpm-list");

  exit(0);
}
include('rpm2.inc');

var third_party_support = get_kb_item('Host/OS/extended-third-party');
if (empty_or_null(third_party_support) || third_party_support != 'TuxCare') exit(0, 'TuxCare support not enabled.');

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) || 'CentOS Linux' >!< os_product) audit(AUDIT_OS_NOT, 'CentOS Linux');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'CentOS Linux');
if (! preg(pattern:"^7([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'CentOS Linux 7', 'CentOS Linux ' + os_version);

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

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('aarch64' >!< cpu && cpu !~ "^i[3-6]86$" && 'x86_64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'CentOS Linux', cpu);


var constraints = [
  {
    'release': '7',
    'pkgs': [
      {'reference':'unbound-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'aarch64', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'i686', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'x86_64', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-devel-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'aarch64', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-devel-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'i686', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-devel-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'x86_64', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-libs-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'aarch64', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-libs-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'i686', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-libs-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'x86_64', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-python-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'aarch64', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-python-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'i686', 'el_string':'el7_8', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'unbound-python-1.6.6-5.0.1.el7_8.tuxcare.els2', 'cpu':'x86_64', 'el_string':'el7_8', '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, 'unbound / unbound-devel / unbound-libs / unbound-python');
}