TencentOS Server 4: nginx (TSSA-2026:0673)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Tencent Linux Security Advisory TSSA-2026:0673.
##

include('compat.inc');

if (description)
{
  script_id(330774);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/07/29");

  script_cve_id("CVE-2026-42533");
  script_xref(name:"IAVA", value:"2026-A-0754");

  script_name(english:"TencentOS Server 4: nginx (TSSA-2026:0673)");

  script_set_attribute(attribute:"synopsis", value:
"The remote TencentOS Server 4 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 4 host is prior to tested version. It is,
therefore, affected by a vulnerability as referenced in the TSSA-2026:0673 advisory.

    Package updates are available for TencentOS Server 4 that fix the following vulnerabilities:

    CVE-2026-42533:
    A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a
    string expression references the map's regex capture variables before referencing the map output variable.
    An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by
    sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading
    to a restart or possibly code execution on systems with ASLR disabled.

Tenable has extracted the preceding description block directly from the Tencent Linux 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://mirrors.tencent.com/tlinux/errata/tssa-20260673.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:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss4_vector", value:"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:P");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-42533");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/07/15");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/07/28");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/07/29");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:tencent:tencentos_server:4");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:tencent:tencentos_server:nginx");
  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:"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:"^4([^0-9]|$)", string:os_version)) audit(AUDIT_OS_NOT, 'TencentOS 4.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': '4',
    'pkgs': [
      {'reference':'nginx-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-all-modules-1.26.3-1.tl4.ap.7', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-core-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-core-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-core-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-core-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-debugsource-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-debugsource-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-filesystem-1.26.3-1.tl4.ap.7', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-devel-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-devel-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-image-filter-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-image-filter-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-image-filter-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-image-filter-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-perl-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-perl-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-perl-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-perl-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-xslt-filter-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-xslt-filter-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-xslt-filter-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-http-xslt-filter-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-mail-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-mail-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-mail-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-mail-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-stream-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-stream-1.26.3-1.tl4.ap.7', 'cpu':'x86_64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-stream-debuginfo-1.26.3-1.tl4.ap.7', 'cpu':'aarch64', 'rpm_spec_vers_cmp':TRUE},
      {'reference':'nginx-mod-stream-debuginfo-1.26.3-1.tl4.ap.7', '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, 'nginx / nginx-all-modules / nginx-core / etc');
}