LOYTEC L-IP BACnet/IP Routers Unchecked Input for Loop Condition (CVE-2026-55731)

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

include('compat.inc');

if (description)
{
  script_id(505947);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/07");

  script_cve_id("CVE-2026-55731");

  script_name(english:"LOYTEC L-IP BACnet/IP Routers Unchecked Input for Loop Condition (CVE-2026-55731)");

  script_set_attribute(attribute:"synopsis", value:
"The remote OT asset is affected by a vulnerability.");
  script_set_attribute(attribute:"description", value:
"The SNMP agent of a LOYTEC L-IP BACnet/IP router does not bound
the loop condition it derives from an SNMP GETNEXT request's
OID. An unauthenticated remote attacker can send a crafted
GETNEXT request containing an oversized OID component to drive
the agent into a long-running loop, exhausting CPU resources
and causing a persistent denial of service.

This plugin only works with Tenable.ot.
Please visit https://www.tenable.com/products/tenable-ot for more information.");
  # https://www.loytec.com/support/product-security/advisories/8531-dibt-cve-20260601-0003-unchecked-input-for-loop-condition-cwe-606-in-the-snmp-agent-medium
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?7aec66ed");
  script_set_attribute(attribute:"solution", value:
"Upgrade to firmware version 8.4.18 or later.");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H");
  script_set_attribute(attribute:"cvss4_vector", value:"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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-2026-55731");

  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:"2026/07/03");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/07/03");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/07");

  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:loytec:lip-me201c_firmware");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:loytec:lip-me202c_firmware");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:loytec:lip-me204c_firmware");
  script_set_attribute(attribute:"generated_plugin", value:"former");
  script_cwe_id(606);
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Tenable.ot");

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

  script_dependencies("tenable_ot_api_integration.nasl");
  script_require_keys("Tenable.ot/LOYTECElectronics");

  exit(0);
}


include('tenable_ot_cve_funcs.inc');

get_kb_item_or_exit('Tenable.ot/LOYTECElectronics');

var asset = tenable_ot::assets::get(vendor:'LOYTECElectronics');

var vuln_cpes = {
    "cpe:/o:loytec:lip-me201c_firmware" :
        {"versionEndExcluding" : "8.4.18", "family" : "LIPBacnetRouters"},
    "cpe:/o:loytec:lip-me202c_firmware" :
        {"versionEndExcluding" : "8.4.18", "family" : "LIPBacnetRouters"},
    "cpe:/o:loytec:lip-me204c_firmware" :
        {"versionEndExcluding" : "8.4.18", "family" : "LIPBacnetRouters"}
};

tenable_ot::cve::compare_and_report(asset:asset, cpes:vuln_cpes, severity:SECURITY_HOLE);