CVE-2026-71256: Debevv Nanomodbus

Critical severity, CVSS 9.8. EPSS: 0.6% chance of exploitation in the next 30 days.

nanoMODBUS through v1.23.0 contains an out-of-bounds stack read leading to a wild-pointer write in nmbs_read_device_identification_basic / recv_read_device_identification_res in nanomodbus.c. A fixed 3-element stack array order[3] = {0,1,2} maps object IDs to buffer indices. The server-supplied object_id field (0-255, read directly from the wire) is used without any bounds check as buf_index = order[object_id].

Affected products

• Debevv Nanomodbus: up to and including 1.23.0

Published 2026-08-05. Last modified 2026-08-26.