Amazon Linux 2 : tigervnc, --advisory ALAS2-2026-3792 (ALAS-2026-3792)

#%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-2026-3792.
##

include('compat.inc');

if (description)
{
  script_id(325583);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/07/08");

  script_cve_id("CVE-2026-50259");

  script_name(english:"Amazon Linux 2 : tigervnc, --advisory ALAS2-2026-3792 (ALAS-2026-3792)");

  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 tigervnc installed on the remote host is prior to 1.8.0-24. It is, therefore, affected by a vulnerability
as referenced in the ALAS2-2026-3792 advisory.

    A stack-based buffer overflow flaw was found in the X.Org X server and Xwayland. _XkbSetMapChecks()
    declares a fixed-size stack buffer mapWidths[256] indexed by key type index. The helper function
    CheckKeyTypes() writes to this buffer at a client-controlled offset, allowing a stack buffer overflow.
    This may be used to crash the server, or for privilege escalation if the X server runs as root.
    (CVE-2026-50259)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue 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/ALAS2-2026-3792.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-2026-50259.html");
  script_set_attribute(attribute:"solution", value:
"Run 'yum update tigervnc' or
  or 'yum update --advisory ALAS2-2026-3792' to update your system.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/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:L/AC:L/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-2026-50259");

  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:"2026/06/01");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/07/08");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/07/08");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:tigervnc");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:tigervnc-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:tigervnc-icons");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:tigervnc-license");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:tigervnc-server");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:tigervnc-server-applet");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:tigervnc-server-minimal");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:tigervnc-server-module");
  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':'tigervnc-1.8.0-24.amzn2.0.10', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-1.8.0-24.amzn2.0.10', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-1.8.0-24.amzn2.0.10', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-debuginfo-1.8.0-24.amzn2.0.10', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-debuginfo-1.8.0-24.amzn2.0.10', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-debuginfo-1.8.0-24.amzn2.0.10', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-icons-1.8.0-24.amzn2.0.10', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-license-1.8.0-24.amzn2.0.10', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-1.8.0-24.amzn2.0.10', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-1.8.0-24.amzn2.0.10', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-1.8.0-24.amzn2.0.10', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-applet-1.8.0-24.amzn2.0.10', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-minimal-1.8.0-24.amzn2.0.10', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-minimal-1.8.0-24.amzn2.0.10', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-minimal-1.8.0-24.amzn2.0.10', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-module-1.8.0-24.amzn2.0.10', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-module-1.8.0-24.amzn2.0.10', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'tigervnc-server-module-1.8.0-24.amzn2.0.10', '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_WARNING,
      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, "tigervnc / tigervnc-debuginfo / tigervnc-icons / etc");
}