debevv nanoMODBUS up to 1.23.0 Modbus nanomodbus.c nmbs_read_device_identification_basic object_id out-of-bounds

Summaryinfo

A vulnerability identified as critical has been detected in debevv nanoMODBUS up to 1.23.0. This affects the function nmbs_read_device_identification_basic of the file nanomodbus.c of the component Modbus Handler. This manipulation of the argument object_id causes out-of-bounds. This vulnerability is registered as CVE-2026-71256. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability has been found in debevv nanoMODBUS up to 1.23.0 and classified as critical. Affected by this vulnerability is the function nmbs_read_device_identification_basic of the file nanomodbus.c of the component Modbus Handler. The manipulation of the argument object_id with an unknown input leads to a out-of-bounds vulnerability. The CWE definition for the vulnerability is CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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]. When a malicious Modbus server sends a Read Device Identification response with object_id >= 3, this reads an out-of-bounds/garbage byte from the stack adjacent to order[], which is then used as an index into a 3-element buffers[] array of char* pointers. The resulting wild pointer is passed to strncpy() as the destination, causing an arbitrary-address write with server-controlled data.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-71256 since 08/05/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/05/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• debevv

Name

• nanoMODBUS

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23.0

CPE 2.3info

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CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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