Apache Log4j 2.13.1 < 2.25.5 / 2.26.0 < 2.26.1 Improper JSON Serialization (CVE-2026-49844)

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

include('compat.inc');

if (description)
{
  script_id(327598);
  script_version("1.3");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/07/20");

  script_cve_id("CVE-2026-49844");
  script_xref(name:"IAVA", value:"2026-A-0688");

  script_name(english:"Apache Log4j 2.13.1 < 2.25.5 / 2.26.0 < 2.26.1 Improper JSON Serialization (CVE-2026-49844)");

  script_set_attribute(attribute:"synopsis", value:
"A logging library installed on the remote host is affected by an improper output encoding vulnerability.");
  script_set_attribute(attribute:"description", value:
"The version of Apache Log4j on the remote host is affected by a vulnerability:

  - Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j
    API produces output that is not valid JSON. When a MapMessage contains a non-finite IEEE 754 value (NaN,
    Infinity, or -Infinity), MapMessage.asJson() emits the corresponding bare token. RFC 8259 does not permit
    these tokens, so a conformant parser rejects the resulting document. An attacker who can supply a non-finite
    value can cause the affected layout to emit malformed JSON, which may corrupt the enclosing log record or
    disrupt downstream log ingestion and parsing. (CVE-2026-49844)

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://logging.apache.org/security.html#CVE-2026-49844");
  script_set_attribute(attribute:"solution", value:
"Upgrade to Apache Log4j version 2.25.5 or 2.26.1 or later. For other branches, upgrade to a fixed version when available.");
  script_set_attribute(attribute:"agent", value:"all");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:H/Au:N/C:N/I:C/A:N");
  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:N/S:U/C:N/I:H/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss4_vector", value:"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:U");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-49844");

  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:"2026/07/10");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/07/10");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/07/17");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:apache:log4j");
  script_set_attribute(attribute:"stig_severity", value:"I");
  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("apache_log4j_nix_installed.nbin", "apache_log4j_win_installed.nbin");
  script_require_keys("installed_sw/Apache Log4j");

  exit(0);
}

include('vdf.inc');

# @tvdl-content
var vuln_data = {
  'metadata': {'spec_version': '1.0'},
  'checks': [
    {
      'product': {'name': 'Apache Log4j', 'type': 'app'},
      'check_algorithm': 'default',
      'constraints': [
        {'min_version': '2.13.1', 'fixed_version': '2.25.5'},
        {'min_version': '2.26.0', 'fixed_version': '2.26.1'},
        {'min_version': '3.0.0-alpha1', 'max_version': '3.0.0-beta2',
         'fixed_display': 'See vendor advisory'}
      ]
    }
  ]
};

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