CVE-2026-71254 CRITICAL

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

Vendor Debevv
Product nanoMODBUS
Weakness CWE-787
Published August 5, 2026
Last update August 10, 2026
View on NVD All CVEs

CVSS base score

9.8/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality High
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

August 5, 2026 CVE published
August 10, 2026 Record updated