Amazon Linux 2023 : perl-Net-DNS, perl-Net-DNS-Nameserver, perl-Net-DNS-tests (ALAS2023-2026-2046)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Amazon Linux 2023 Security Advisory ALAS2023-2026-2046.
##

include('compat.inc');

if (description)
{
  script_id(337214);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/18");

  script_cve_id("CVE-2026-64193", "CVE-2026-64194");

  script_name(english:"Amazon Linux 2023 : perl-Net-DNS, perl-Net-DNS-Nameserver, perl-Net-DNS-tests (ALAS2023-2026-2046)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Amazon Linux 2023 host is missing a security update.");
  script_set_attribute(attribute:"description", value:
"It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2046 advisory.

    Net::DNS versions through 1.55 for Perl allow remote execution injection via EDNS EXTENDED ERROR.

    Net::DNS::RR::OPT::EXTENDED_ERROR::_decompose parses the EXTRA-TEXT field of an EDNS EXTENDED-ERROR option
    (RFC 8914) by tokenising the raw bytes and passing the result to Perl's eval. There is some escaping done
    for $ and @, but not for backticks. This can be exploited for command execution if
    $pkt->edns->option('EXTENDED-ERROR') is called in array context, for example with a payload of
    {0:`<command>`} in EXTRA-TEXT. (CVE-2026-64193)

    Net::DNS versions through 1.55 for Perl allow Denial of Service via deep DNS compression pointer chains.

    Net::DNS::DomainName::decode follows RFC 1035 compression pointers by recursing into itself with no depth
    limit. It is possible to construct a name which saturates the call stack (at least with larger TCP
    responses), leading to a potential Denial of Service.

    The guard `$link < $offset` prevents forward and circular chains, but still allows arbitrarily long
    backward chains. The per-offset cache (`$cache`) is populated at the start of each call and short-circuits
    only re-traverses of the same offset - the initial descent through a fresh chain still recurses at full
    depth.

    A crafted packet can chain two-byte compression pointers so that each one points two bytes earlier than
    the previous, producing a chain length of `offset / 2`. For the 14-bit pointer field (max offset 16383)
    this gives up to ~8191 recursive frames. For a TCP DNS message the limit is the 16-bit length field
    (~32767 frames). Perl's default C stack handles only a few thousand frames; beyond that the process
    receives SIGSEGV or similar, which is a denial-of-service for any application parsing untrusted DNS data.

    The vulnerability is triggered by `Net::DNS::Packet->new(\$wire)` i.e. any point where the library decodes
    a DNS message from the network. (CVE-2026-64194)

Tenable has extracted the preceding description block directly from the tested product 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://alas.aws.amazon.com//AL2023/ALAS2023-2026-2046.html");
  script_set_attribute(attribute:"see_also", value:"https://alas.aws.amazon.com/faqs.html");
  script_set_attribute(attribute:"see_also", value:"https://explore.alas.aws.amazon.com/CVE-2026-64193.html");
  script_set_attribute(attribute:"see_also", value:"https://explore.alas.aws.amazon.com/CVE-2026-64194.html");
  script_set_attribute(attribute:"solution", value:
"Run 'dnf update perl-Net-DNS --releasever 2023.12.20260817' or
  or 'dnf update --advisory ALAS2023-2026-2046 --releasever 2023.12.20260817' to update your system.");
  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:"cvss_score_source", value:"CVE-2026-64193");

  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:"2026/07/20");
  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:"cpe", value:"p-cpe:/a:amazon:linux:perl-Net-DNS");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:perl-Net-DNS-Nameserver");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:perl-Net-DNS-tests");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:amazon:linux:2023");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Amazon 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_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/AmazonLinux/release", "Host/AmazonLinux/rpm-list");

  exit(0);
}

include("rpm2.inc");

if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);

var alas_release = get_kb_item("Host/AmazonLinux/release");
if (isnull(alas_release) || !strlen(alas_release)) audit(AUDIT_OS_NOT, "Amazon Linux");
var os_ver = pregmatch(pattern: "^AL(A|\d+|-\d+)", string:alas_release);
if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "Amazon Linux");
os_ver = os_ver[1];
if (os_ver != "-2023")
{
  if (os_ver == 'A') os_ver = 'AMI';
  audit(AUDIT_OS_NOT, "Amazon Linux 2023", "Amazon Linux " + os_ver);
}

if (!get_kb_item("Host/AmazonLinux/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);

var pkgs = [
    {'reference':'perl-Net-DNS-1.56-1.amzn2023.0.1', 'release':'AL-2023', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'perl-Net-DNS-Nameserver-1.56-1.amzn2023.0.1', 'release':'AL-2023', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'perl-Net-DNS-tests-1.56-1.amzn2023.0.1', 'release':'AL-2023', 'rpm_spec_vers_cmp':TRUE}
];

var flag = 0;
foreach var package_array ( pkgs ) {
  var reference = NULL;
  var _release = NULL;
  var sp = NULL;
  var _cpu = NULL;
  var el_string = NULL;
  var rpm_spec_vers_cmp = NULL;
  var epoch = NULL;
  var allowmaj = NULL;
  var exists_check = NULL;
  var cves = NULL;
  if (!empty_or_null(package_array['reference'])) reference = package_array['reference'];
  if (!empty_or_null(package_array['release'])) _release = package_array['release'];
  if (!empty_or_null(package_array['sp'])) sp = package_array['sp'];
  if (!empty_or_null(package_array['cpu'])) _cpu = package_array['cpu'];
  if (!empty_or_null(package_array['el_string'])) el_string = package_array['el_string'];
  if (!empty_or_null(package_array['rpm_spec_vers_cmp'])) rpm_spec_vers_cmp = package_array['rpm_spec_vers_cmp'];
  if (!empty_or_null(package_array['epoch'])) epoch = package_array['epoch'];
  if (!empty_or_null(package_array['allowmaj'])) allowmaj = package_array['allowmaj'];
  if (!empty_or_null(package_array['exists_check'])) exists_check = package_array['exists_check'];
  if (!empty_or_null(package_array['cves'])) cves = package_array['cves'];
  if (reference && _release && (!exists_check || rpm_exists(release:_release, rpm:exists_check))) {
    if (rpm_check(release:_release, 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, "perl-Net-DNS / perl-Net-DNS-Nameserver / perl-Net-DNS-tests");
}