Amazon Linux 2 : python-kdcproxy, --advisory ALAS2-2025-3085 (ALAS-2025-3085)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Amazon Linux 2 Security Advisory ALAS-2025-3085.
##

include('compat.inc');

if (description)
{
  script_id(277753);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2025/12/08");

  script_cve_id("CVE-2025-59088", "CVE-2025-59089");

  script_name(english:"Amazon Linux 2 : python-kdcproxy, --advisory ALAS2-2025-3085 (ALAS-2025-3085)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Amazon Linux 2 host is missing a security update.");
  script_set_attribute(attribute:"description", value:
"The version of python-kdcproxy installed on the remote host is prior to 0.3.3-1. It is, therefore, affected by multiple
vulnerabilities as referenced in the ALAS2-2025-3085 advisory.

    If kdcproxy receives a request for a realm which does not have server addresses defined in its
    configuration, by default, it will query SRV records in the DNS zone matching the requested realm name.
    This creates a server-side request forgery vulnerability, since an attacker could send a request for a
    realm matching a DNS zone where they created SRV records pointing to arbitrary ports and hostnames (which
    may resolve to loopback or internal IP addresses). This vulnerability can be exploited to probe internal
    network topology and firewall rules, perform port scanning, and exfiltrate data. Deployments where the
    use_dns setting is explicitly set to false are not affected. (CVE-2025-59088)

    If an attacker causes kdcproxy to connect to an attacker-controlled KDC server (e.g. through server-side
    request forgery), they can exploit the fact that kdcproxy does not enforce bounds on TCP response length
    to conduct a denial-of-service attack. While receiving the KDC's response, kdcproxy copies the entire
    buffered stream into a newbuffer on each recv() call, even when the transfer is incomplete, causing
    excessive memory allocation and CPU usage. Additionally, kdcproxy accepts incoming response chunks as long
    as the received data length is not exactly equal to the length indicated in the responseheader, even when
    individual chunks or the total buffer exceed the maximum length of a Kerberos message. This allows an
    attacker to send unbounded data until the connection timeout is reached (approximately 12 seconds),
    exhausting server memory or CPU resources. Multiple concurrent requests can cause accept queue overflow,
    denying service to legitimate clients. (CVE-2025-59089)

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//AL2/ALAS2-2025-3085.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-2025-59088.html");
  script_set_attribute(attribute:"see_also", value:"https://explore.alas.aws.amazon.com/CVE-2025-59089.html");
  script_set_attribute(attribute:"solution", value:
"Run 'yum update python-kdcproxy' or
  or 'yum update --advisory ALAS2-2025-3085' to update your system.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:C/I:N/A:N");
  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:C/C:H/I:N/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2025-59088");

  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:"2025/11/12");
  script_set_attribute(attribute:"patch_publication_date", value:"2025/12/08");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/12/08");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:python-kdcproxy");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:amazon:linux:2");
  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) 2025 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("rpm.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 != "2")
{
  if (os_ver == 'A') os_ver = 'AMI';
  audit(AUDIT_OS_NOT, "Amazon Linux 2", "Amazon Linux " + os_ver);
}

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

var pkgs = [
    {'reference':'python-kdcproxy-0.3.3-1.amzn2.0.1', 'release':'AL2', '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, "python-kdcproxy");
}