Amazon Linux 2 : 389-ds-base (ALAS-2026-3957)

#%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-2026-3957.
##

include('compat.inc');

if (description)
{
  script_id(351082);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/29");

  script_cve_id("CVE-2026-18355", "CVE-2026-18453");

  script_name(english:"Amazon Linux 2 : 389-ds-base (ALAS-2026-3957)");

  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 389-ds-base installed on the remote host is prior to 1.3.10.2-17. It is, therefore, affected by multiple
vulnerabilities as referenced in the ALAS2-2026-3957 advisory.

    A heap buffer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base). In
    sasl_io_start_packet(), the wrapped-record length read from the wire is validated only against an upper
    bound. A small wire length (0, 1, or 2) produces an encrypted_buffer_count below the already-consumed
    encrypted_buffer_offset, causing an unsigned subtraction underflow in sasl_io_read_packet(). PR_Recv is
    then requested to read approximately 4 GiB into a 1024-byte heap buffer, resulting in a heap buffer
    overflow with attacker-controlled content. After a successful SASL bind with integrity protection (SSF >
    0), a remote authenticated attacker can cause a denial of service or potentially achieve remote code
    execution. This flaw is distinct from CVE-2026-11774, whose fix only guards against upper-bound overflow.
    (CVE-2026-18355)

    A flaw was found in 389 Directory Server. A missing NULL pointer check in the paged results handling of
    op_shared_search allows an unauthenticated remote attacker to crash the LDAP server by sending a crafted
    sequence of search requests using the USE_ONE_BACKEND control, resulting in denial of service.
    (CVE-2026-18453)

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/ALAS2-2026-3957.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-2026-18355.html");
  script_set_attribute(attribute:"see_also", value:"https://explore.alas.aws.amazon.com/CVE-2026-18453.html");
  script_set_attribute(attribute:"solution", value:
"Run 'yum update 389-ds-base' or
  or 'yum update --advisory ALAS2-2026-3957' to update your system.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:H/Au:S/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:H/PR:L/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-2026-18355");

  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:"2026/09/07");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/09/28");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/29");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:389-ds-base");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:389-ds-base-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:389-ds-base-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:389-ds-base-libs");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:389-ds-base-snmp");
  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) 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 != "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':'389-ds-base-1.3.10.2-17.amzn2.0.12', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-1.3.10.2-17.amzn2.0.12', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-1.3.10.2-17.amzn2.0.12', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-debuginfo-1.3.10.2-17.amzn2.0.12', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-debuginfo-1.3.10.2-17.amzn2.0.12', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-debuginfo-1.3.10.2-17.amzn2.0.12', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-devel-1.3.10.2-17.amzn2.0.12', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-devel-1.3.10.2-17.amzn2.0.12', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-devel-1.3.10.2-17.amzn2.0.12', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-libs-1.3.10.2-17.amzn2.0.12', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-libs-1.3.10.2-17.amzn2.0.12', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-libs-1.3.10.2-17.amzn2.0.12', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-snmp-1.3.10.2-17.amzn2.0.12', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-snmp-1.3.10.2-17.amzn2.0.12', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'389-ds-base-snmp-1.3.10.2-17.amzn2.0.12', 'cpu':'x86_64', '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, "389-ds-base / 389-ds-base-debuginfo / 389-ds-base-devel / etc");
}