The vulnerability in nanoMODBUS through version 1.23.0 arises from improper bounds checking on the server-supplied object_id field (0-255) used as an index into a fixed 3-element stack array order[3]. This results in an out-of-bounds stack read and subsequent wild-pointer write in nanomodbus.c functions nmbs_read_device_identification_basic and recv_read_device_identification_res. The lack of validation allows an attacker to cause memory corruption, potentially leading to arbitrary code execution or denial of service.

Successful exploitation can lead to memory corruption due to wild-pointer writes, impacting confidentiality, integrity, and availability of the affected system. The CVSS score of 9.8 reflects critical severity with network attack vector, no privileges required, no user interaction, and full impact on confidentiality, integrity, and availability.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should consider restricting access to the nanoMODBUS service from untrusted networks to reduce exposure.