TencentOS Server 3: libXfont2 (TSSA-2026:0901)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Tencent Linux Security Advisory TSSA-2026:0901.
##

include('compat.inc');

if (description)
{
  script_id(341109);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/27");

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

  script_name(english:"TencentOS Server 3: libXfont2 (TSSA-2026:0901)");

  script_set_attribute(attribute:"synopsis", value:
"The remote TencentOS Server 3 host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The version of Tencent Linux installed on the remote TencentOS Server 3 host is prior to tested version. It is,
therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:0901 advisory.

    Package updates are available for TencentOS Server 3 that fix the following vulnerabilities:

    CVE-2026-44950:
    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-2026-59679:
    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.

Tenable has extracted the preceding description block directly from the Tencent Linux 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://mirrors.tencent.com/tlinux/errata/tssa-20260901.xml");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages.");
  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:"2026/08/17");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/27");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:tencent:tencentos_server:3");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:tencent:tencentos_server:libXfont2");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Tencent 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/etc/os-release", "Host/TencentOS/rpm-list", "Host/cpu");

  exit(0);
}


include('rpm2.inc');

if (!get_kb_item('Host/local_checks_enabled')) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_product = get_kb_item('installed_os/local/SSH/0/product');
if (isnull(os_product) || 'TencentOS' >!< os_product) audit(AUDIT_OS_NOT, 'TencentOS');
var os_version = get_kb_item('installed_os/local/SSH/0/version');
if (isnull(os_version)) audit(AUDIT_UNKNOWN_APP_VER, 'TencentOS');
if (! preg(pattern:"^3([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'TencentOS 3.x', 'TencentOS ' + os_version);

if (!get_kb_item('Host/TencentOS/rpm-list')) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 's390' >!< cpu && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'TencentOS', cpu);

var constraints = [
  {
    'release': '3',
    'pkgs': [
      {'reference':'libXfont2-2.0.3-2.tl3.3', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libXfont2-2.0.3-2.tl3.3', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libXfont2-debuginfo-2.0.3-2.tl3.3', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libXfont2-debuginfo-2.0.3-2.tl3.3', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libXfont2-debugsource-2.0.3-2.tl3.3', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libXfont2-debugsource-2.0.3-2.tl3.3', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libXfont2-devel-2.0.3-2.tl3.3', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'libXfont2-devel-2.0.3-2.tl3.3', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE}
    ]
  }
];

var os_release = get_one_kb_item('installed_os/local/SSH/0/release');
var os_sp = get_one_kb_item('Host/*/minor_release');

var flag = 0;
var reference;
var sp;
var _cpu;
var el_string;
var rpm_spec_vers_cmp;
var epoch;
var allowmaj;
var exists_check;
var cves;
foreach var constraint ( constraints ) {
  # Check that the target release is equal to the affected release
  if (!empty_or_null(constraint['release'])){
    if (constraint['release'] != os_release) continue;
  }
  if (!empty_or_null(constraint['sp'])){
    if (constraint['sp'] != os_sp) continue;
  }
  foreach var pkg ( constraint['pkgs'] ) {
    reference = NULL;
    sp = NULL;
    _cpu = NULL;
    el_string = NULL;
    rpm_spec_vers_cmp = NULL;
    epoch = NULL;
    allowmaj = NULL;
    exists_check = NULL;
    cves = NULL;
    if (!empty_or_null(pkg['reference'])) reference = pkg['reference'];
    if (!empty_or_null(pkg['sp'])) sp = pkg['sp'];
    if (!empty_or_null(pkg['cpu'])) _cpu = pkg['cpu'];
    if (!empty_or_null(pkg['el_string'])) el_string = pkg['el_string'];
    if (!empty_or_null(pkg['rpm_spec_vers_cmp'])) rpm_spec_vers_cmp = pkg['rpm_spec_vers_cmp'];
    if (!empty_or_null(pkg['epoch'])) epoch = pkg['epoch'];
    if (!empty_or_null(pkg['allowmaj'])) allowmaj = pkg['allowmaj'];
    if (!empty_or_null(pkg['exists_check'])) exists_check = pkg['exists_check'];
    if (!empty_or_null(pkg['cves'])) cves = pkg['cves'];
    if (reference &&
        ## (no known rpm to check OR known rpm_exists)
        (!exists_check || rpm_exists(rpm:exists_check)) &&
        rpm_check(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, 'libXfont2 / libXfont2-debuginfo / libXfont2-debugsource / etc');
}