Amazon Linux 2 : nerdctl (ALAS-2026-4018)

#%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-2026-4018.
##

include('compat.inc');

if (description)
{
  script_id(371758);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/24");

  script_cve_id(
    "CVE-2026-56855",
    "CVE-2026-78659",
    "CVE-2026-78662",
    "CVE-2026-78663"
  );
  script_xref(name:"IAVB", value:"2026-B-0296-S");

  script_name(english:"Amazon Linux 2 : nerdctl (ALAS-2026-4018)");

  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 nerdctl installed on the remote host is prior to 2.3.5-1. It is, therefore, affected by multiple
vulnerabilities as referenced in the ALAS2-2026-4018 advisory.

    Previously, after a channel has been established, a malicious peer could send crafted messages that would
    deadlock the entire connection. Now, we handle all RFC 4254 channel messages; global requests are handled
    explicitly. Then, treat all other messages as a protocol error and tear the connection down instead of
    buffering and blocking. (CVE-2026-56855)

    When Trailer headers are sent by a client, the HTTP server internally uses the header values to populate
    the Request.Trailer map passed to the server handler. Because Request.Trailer is a map, each entry incurs
    memory overhead. For HTTP/2 servers, a malicious client can exploit this by sending a Trailer header
    that declares a large number of fields causing the server to allocate a disproportionate amount of memory
    while bypassing Server.MaxHeaderValueCount and Server.MaxHeaderBytes limits.This exploit is not applicable
    for HTTP/1 servers, which do not support  multiplexing a large number of requests over one TCP connection,
    and whose Server.MaxHeaderBytes are calculated differently.Server.MaxHeaderValueCount and
    Server.MaxHeaderBytes limits are now applied towards the trailer fields declared in Trailer headers.

    NOTE: https://www.openwall.com/lists/oss-security/2026/10/08/9NOTE:
    https://github.com/golang/go/issues/81857NOTE: Fixed by:
    https://github.com/golang/go/commit/cbb0fb8b51cba866018b8a0fb4b5458f16c5c80b (go1.27.2)NOTE: Fixed by:
    https://github.com/golang/go/commit/6e049521882c944afc1e519a83971ec421dc2974 (go1.26.9) (CVE-2026-78659)

    Previously, a channel registered in the mux's chanList is not usable until it is established. A malicious
    peer was able flood the channel's incomingRequests, deadlocking the entire connection. Now, we add an
    atomic established state, set when a channel becomes usable. Until such a time, handlePacket drops every
    packet other than the open confirmation/failure, without blocking and without tearing down the connection.
    (CVE-2026-78662)

    The HTTP/2 server could refund connection-level flow control twice for the same data: Once when a client
    resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request
    handler reads the buffered data.A malicious client could exploit this to bypass the configured connection-
    level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the
    concurrent stream limit and stream-level flow control.The HTTP/2 server now waits to refund connection-
    level flow control for reset streams until after the request handler is complete.

    NOTE: https://www.openwall.com/lists/oss-security/2026/10/08/9NOTE:
    https://github.com/golang/go/issues/81743NOTE: Fixed by:
    https://github.com/golang/go/commit/31dc9e2449e394439498142451627af52626d7c4 (go1.27.2)NOTE: Fixed by:
    https://github.com/golang/go/commit/6e049521882c944afc1e519a83971ec421dc2974 (go1.26.9) (CVE-2026-78663)

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/ALAS2-2026-4018.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-2026-56855.html");
  script_set_attribute(attribute:"see_also", value:"https://explore.alas.aws.amazon.com/CVE-2026-78659.html");
  script_set_attribute(attribute:"see_also", value:"https://explore.alas.aws.amazon.com/CVE-2026-78662.html");
  script_set_attribute(attribute:"see_also", value:"https://explore.alas.aws.amazon.com/CVE-2026-78663.html");
  script_set_attribute(attribute:"solution", value:
"Run 'yum update nerdctl' or
  or 'yum update --advisory ALAS2-2026-4018' to update your system.");
  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:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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-2026-78663");

  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:"2026/09/02");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/10/24");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/24");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:nerdctl");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:nerdctl-debuginfo");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:amazon:linux:2");
  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:"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_info2.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':'nerdctl-2.3.5-1.amzn2.0.2', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'nerdctl-2.3.5-1.amzn2.0.2', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'nerdctl-debuginfo-2.3.5-1.amzn2.0.2', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'nerdctl-debuginfo-2.3.5-1.amzn2.0.2', '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, "nerdctl / nerdctl-debuginfo");
}