nanoMODBUS Client-Side Out-of-Bounds Write via object_length in recv_read_device_identification_res()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-71255
StatePUBLISHED
AssignerTuranSec
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-05 12:18:57 UTC
Updated2026-08-05 13:24:49 UTC
DescriptionnanoMODBUS through v1.23.0 contains an out-of-bounds write in the Modbus client-side recv_read_device_identification_res() function (FC 0x2B/MEI 0x0E, Read Device Identification) in nanomodbus.c. The server-supplied object_length field (0-246) is validated only against the remaining PDU size (res_size_left) and is never validated against the caller-supplied buffers_length parameter. After copying data with strncpy(buffers_out[buf_index], str, buffers_length), the code unconditionally writes a NUL terminator at buffers_out[buf_index][object_length]. When a malicious or compromised Modbus server sends a response with object_length greater than or equal to the client's buffers_length, this NUL write lands past the end of the caller-provided buffer, corrupting adjacent stack or heap memory on the client.

Risk And Classification

Primary CVSS: v3.1 8.6 HIGH from 309f9ea4-e3e9-4c6c-b79d-e8eb01244f2c

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

Problem Types: CWE-787 | CWE-787 CWE-787

VersionSourceTypeScoreSeverityVector
3.1309f9ea4-e3e9-4c6c-b79d-e8eb01244f2cSecondary8.6HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
3.1CNADECLARED8.6HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Debevv NanoMODBUS affected 1.23.0 semver Not specified

References

ReferenceSourceLinkTags
github.com/debevv/nanoMODBUS/blob/master/nanomodbus.c 309f9ea4-e3e9-4c6c-b79d-e8eb01244f2c github.com
github.com/debevv/nanoMODBUS 309f9ea4-e3e9-4c6c-b79d-e8eb01244f2c github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Shukhratbek Uraiimov (en)

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