Amazon Linux 2 : libXfont, --advisory ALAS2-2026-3890 (ALAS-2026-3890)

#%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-2026-3890.
##

include('compat.inc');

if (description)
{
  script_id(341894);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/31");

  script_cve_id("CVE-2026-44950", "CVE-2026-59679");

  script_name(english:"Amazon Linux 2 : libXfont, --advisory ALAS2-2026-3890 (ALAS-2026-3890)");

  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 libXfont installed on the remote host is prior to 1.5.4-1. It is, therefore, affected by multiple
vulnerabilities as referenced in the ALAS2-2026-3890 advisory.

    A flaw was found in the libXfont2 font-server client. This heap buffer overflow vulnerability allows a
    malicious font server to send specially crafted glyph data. The fs_read_glyphs() function fails to
    properly validate the total size of the incoming data, leading to an overwrite of memory beyond the
    intended buffer. If the X server runs as a privileged user, this could result in privilege escalation,
    allowing an attacker to gain higher access. If the X server runs as an unprivileged user, it could lead to
    a denial of service, causing the system to crash. (CVE-2026-44950)

    A flaw was found in the libXfont2 font-server client. A remote attacker, by operating a malicious font
    server, could exploit an out-of-bounds read/write vulnerability. This occurs because the client
    incorrectly handles font data, leading to an out-of-bounds memory access. This can lead to privilege
    escalation if the X server runs with root privileges, or a denial of service (crash) if it runs as an
    unprivileged user. (CVE-2026-59679)

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/ALAS2-2026-3890.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-2026-44950.html");
  script_set_attribute(attribute:"see_also", value:"https://explore.alas.aws.amazon.com/CVE-2026-59679.html");
  script_set_attribute(attribute:"solution", value:
"Run 'yum update libXfont' or
  or 'yum update --advisory ALAS2-2026-3890' to update your system.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:H/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:H/PR:N/UI:R/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-2026-59679");

  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:"2026/08/05");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/08/31");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/31");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:libXfont");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:libXfont-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:libXfont-devel");
  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':'libXfont-1.5.4-1.amzn2.0.2', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'libXfont-1.5.4-1.amzn2.0.2', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'libXfont-1.5.4-1.amzn2.0.2', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'libXfont-debuginfo-1.5.4-1.amzn2.0.2', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'libXfont-debuginfo-1.5.4-1.amzn2.0.2', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'libXfont-debuginfo-1.5.4-1.amzn2.0.2', 'cpu':'x86_64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'libXfont-devel-1.5.4-1.amzn2.0.2', 'cpu':'aarch64', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'libXfont-devel-1.5.4-1.amzn2.0.2', 'cpu':'i686', 'release':'AL2', 'rpm_spec_vers_cmp':TRUE},
    {'reference':'libXfont-devel-1.5.4-1.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, "libXfont / libXfont-debuginfo / libXfont-devel");
}