nginx 0.3.50 < 1.30.3 / 1.31.x < 1.31.2 Buffer Overread in ngx_http_charset_module

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

include('compat.inc');

if (description)
{
  script_id(321915);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/06/23");

  script_cve_id("CVE-2026-48142");
  script_xref(name:"IAVA", value:"2026-A-0601");

  script_name(english:"nginx 0.3.50 < 1.30.3 / 1.31.x < 1.31.2 Buffer Overread in ngx_http_charset_module");

  script_set_attribute(attribute:"synopsis", value:
"The remote web server is affected by a vulnerability.");
  script_set_attribute(attribute:"description", value:
"The installed version of nginx is 0.3.50 prior to 1.30.3, or 1.31.x prior to 1.31.2. It is, therefore, affected by
the following issue :

  - NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_charset_module module. When content is
    served or proxied through a location block with both source_charset utf-8; and a charset directive (for example,
    charset koi8-r;) configured, remote, unauthenticated attackers can send requests (in conjunction with conditions
    beyond their control) to cause a heap buffer over-read in the NGINX worker process, leading to limited disclosure
    of memory or a restart. Note: Software versions which have reached End of Technical Support (EoTS) are not
    evaluated. (CVE-2026-48142)

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://my.f5.com/manage/s/article/K000161585");
  script_set_attribute(attribute:"see_also", value:"https://nginx.org/en/security_advisories.html");
  script_set_attribute(attribute:"solution", value:
"Upgrade to nginx 1.30.3 / 1.31.2 or later.");
  script_set_attribute(attribute:"agent", value:"unix");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:H/Au:N/C:P/I:N/A:P");
  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:L/I:N/A:L");
  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:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:U");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-48142");

  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:"2026/06/17");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/06/17");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/06/22");

  script_set_attribute(attribute:"potential_vulnerability", value:"true");
  script_set_attribute(attribute:"plugin_type", value:"combined");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:nginx:nginx");
  script_set_attribute(attribute:"stig_severity", value:"I");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Web Servers");

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

  script_dependencies("nginx_detect.nasl", "nginx_nix_installed.nbin");
  script_require_keys("Settings/ParanoidReport", "installed_sw/nginx");

  exit(0);
}

include('vcf.inc');
include('http.inc');

# ngx_http_charset_module requires specific configuration (source_charset + charset directives)
if (report_paranoia < 2)
  audit(AUDIT_PARANOID);

var appname = 'nginx';
get_install_count(app_name:appname, exit_if_zero:TRUE);

var app_info = vcf::combined_get_app_info(app:appname);
vcf::check_granularity(app_info:app_info, sig_segments:3);

var constraints = [
  { 'min_version' : '0.3.50', 'fixed_version' : '1.30.3' },
  { 'min_version' : '1.31.0', 'fixed_version' : '1.31.2' }
];
vcf::check_version_and_report(
  app_info:app_info,
  constraints:constraints,
  severity:SECURITY_WARNING
);