Vulnerability · Published Aug 5, 2026 · Assigned by TuranSec

CVE-2026-71256nanoMODBUS Client-Side Out-of-Bounds Read Leading to Wild-Pointer Write via object_id

Critical 9.8

In plain English

A critical-severity out-of-bounds read in nanoMODBUS from debevv. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 46% of all known vulnerabilities).

Severity (CVSS 3.1)9.8Critical

Exploit odds (30 days)0.6%top 53.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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 (as reported)

Vendor	Product	Versions
debevv	nanoMODBUS	0 – through 1.23.0

Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

https://github.com/debevv/nanoMODBUS third-party-advisory
https://github.com/debevv/nanoMODBUS/blob/master/nanomodbus.c third-party-advisory