Alibaba Fastjson 1.2.68 < 1.2.84 RCE (CVE-2026-16723)

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(331911);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/08/05");

  script_cve_id("CVE-2026-16723");

  script_name(english:"Alibaba Fastjson 1.2.68 < 1.2.84 RCE (CVE-2026-16723)");

  script_set_attribute(attribute:"synopsis", value:
"A JSON library installed on the remote host is affected by a remote code execution vulnerability.");
  script_set_attribute(attribute:"description", value:
"The version of Alibaba Fastjson installed on the remote host is 1.2.68 through 1.2.83. It is, therefore, affected by
a remote code execution vulnerability:

  - A remote code execution (RCE) vulnerability exists in fastjson 1.2.68 through 1.2.83. This vulnerability is
    exploitable under fastjson's stock default configuration - no AutoType enablement required, no classpath gadget
    required. (CVE-2026-16723)

Enabling SafeMode (-Dfastjson.parser.safeMode=true, ParserConfig.getGlobalInstance().setSafeMode(true), or
fastjson.properties) or switching to a noneautotype build (e.g. com.alibaba:fastjson:1.2.83_noneautotype) mitigates
this issue without upgrading. Nessus cannot verify the runtime SafeMode configuration, so this finding is flagged as a
potential vulnerability.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  # https://github.com/alibaba/fastjson2/wiki/Security-Advisory:-Remote-Code-Execution-in-fastjson-1.2.68%E2%80%931.2.83
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?c5dabecd");
  script_set_attribute(attribute:"solution", value:
"Upgrade to Alibaba Fastjson version 1.2.84 or later. Alternatively, enable SafeMode
(-Dfastjson.parser.safeMode=true) or switch to a noneautotype build.");
  script_set_attribute(attribute:"agent", value:"all");
  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:C/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-16723");

  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:"2026/07/21");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/07/21");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/08/04");

  script_set_attribute(attribute:"potential_vulnerability", value:"true");
  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:alibaba:fastjson");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Misc.");

  script_copyright(english:"This script is Copyright (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("fastjson_jar_detect.nbin");
  script_require_keys("installed_sw/Alibaba Fastjson", "Settings/ParanoidReport");

  exit(0);
}

include('vdf.inc');

if (report_paranoia < 2)
  audit(AUDIT_PARANOID);

# @tvdl-content
var vuln_data = {
  'metadata': {'spec_version': '1.0'},
  'checks': [
    {
      'product': {'name': 'Alibaba Fastjson', 'type': 'app'},
      'check_algorithm': 'default',
      'potential_vulnerability': {
        'missing_config_check': true
      },
      'requires': [
        {'scope': 'target', 'match': {'paranoia': true}}
      ],
      'constraints': [
        {'min_version': '1.2.68', 'fixed_version': '1.2.84'}
      ]
    }
  ]
};

var vdf_result = vdf::check_and_report(vuln_data:vuln_data, severity:SECURITY_HOLE);
vdf::handle_check_and_report_errors(vdf_result:vdf_result);