CVE WatchAug 5, 2026

CVE-2026-71256

nanoMODBUS through v1.23.0 contains an out-of-bounds stack read leading to a wild-pointer write in nmbs_read_device_identification_basic() /

CVSS

9.8

Critical

EPSS

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KEV

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Exploit Today

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0-100

Published: Aug 5, 2026 · Last modified: Aug 5, 2026 · CWE-125

EPSS · 30d

Not enough EPSS history yet.

Technical 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]. 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.

Official references

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