Vulnerability · Published Aug 5, 2026 · Assigned by TuranSec

CVE-2026-71254nanoMODBUS Server-Side Out-of-Bounds Write in handle_read_file_record()

Critical 9.8

In plain English

A critical-severity out-of-bounds write 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 write in the Modbus server-side handle_read_file_record function (FC 0x14, Read File Record) in nanomodbus.c. The function validates that the total request size does not exceed 245 bytes and that each sub-request's record_length is at most 124, but it never validates the CUMULATIVE response size across all sub-requests before processing them.

Affected products (as reported)

Vendor	Product	Versions
debevv	nanoMODBUS	0 – through 1.23.0

Weakness: CWE-787 · 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