TencentOS Server 4: dnsmasq (TSSA-2026:0344)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Tencent Linux Security Advisory TSSA-2026:0344.
##

include('compat.inc');

if (description)
{
  script_id(319759);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/06/08");

  script_cve_id(
    "CVE-2026-2291",
    "CVE-2026-4890",
    "CVE-2026-4891",
    "CVE-2026-4892",
    "CVE-2026-4893",
    "CVE-2026-5172"
  );
  script_xref(name:"IAVA", value:"2026-A-0450");

  script_name(english:"TencentOS Server 4: dnsmasq (TSSA-2026:0344)");

  script_set_attribute(attribute:"synopsis", value:
"The remote TencentOS Server 4 host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The version of Tencent Linux installed on the remote TencentOS Server 4 host is prior to tested version. It is,
therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:0344 advisory.

    Package updates are available for TencentOS Server 4 that fix the following vulnerabilities:

    CVE-2026-5172:
    A buffer overflow in dnsmasqs extract_addresses() function allows an attacker to trigger a heap out-of-
    bounds read and crash by exploiting a malformed DNS response, enabling extract_name() to advance the
    pointer past the records end.

    CVE-2026-4893:
    An information disclosure vulnerability in dnsmasq allows remote attackers to bypass source checks via a
    crafted DNS packet with RFC 7871 client subnet information.

    CVE-2026-4892:
    A heap-based out-of-bounds write vulnerability in the DHCPv6 implementation of dnsmasq allows local
    attackers to execute arbitrary code with root privileges via a crafted DHCPv6 packet.

    CVE-2026-4891:
    A heap-based out-of-bounds read vulnerability in the DNSSEC validation of dnsmasq allows remote attackers
    to cause a denial of service via a crafted DNS packet.

    CVE-2026-4890:
    A Denial of Service (DoS) vulnerability in the DNSSEC validation of dnsmasq allows remote attackers to
    cause a denial of service via a crafted DNS packet.

    CVE-2026-2291:
    dnsmasqs extract_name() function can be abused to cause a heap buffer overflow, allowing an attacker to
    inject false DNS cache entries, which could result in DNS lookups to redirect to an attacker-controlled IP
    address, or to cause a DoS.

Tenable has extracted the preceding description block directly from the Tencent 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:"https://mirrors.tencent.com/tlinux/errata/tssa-20260344.xml");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:POC/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:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-2291");
  script_set_attribute(attribute:"cvss3_score_source", value:"CVE-2026-4892");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/05/11");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/06/04");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/06/08");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:tencent:tencentos_server:4");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:tencent:tencentos_server:dnsmasq");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_set_attribute(attribute:"stig_severity", value:"I");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Tencent 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/etc/os-release", "Host/TencentOS/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) || 'TencentOS' >!< os_product) audit(AUDIT_OS_NOT, 'TencentOS');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'TencentOS');
if (! preg(pattern:"^4([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'TencentOS 4.x', 'TencentOS ' + os_version);

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

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 's390' >!< cpu && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'TencentOS', cpu);

var constraints = [
  {
    'release': '4',
    'pkgs': [
      {'reference':'dnsmasq-2.89-6.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-2.89-6.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-debuginfo-2.89-6.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-debuginfo-2.89-6.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-debugsource-2.89-6.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-debugsource-2.89-6.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-langpack-2.89-6.tl4', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-utils-2.89-6.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-utils-2.89-6.tl4', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-utils-debuginfo-2.89-6.tl4', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'dnsmasq-utils-debuginfo-2.89-6.tl4', '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, 'dnsmasq / dnsmasq-debuginfo / dnsmasq-debugsource / etc');
}