CVE-2026-71256 - nanoMODBUS Client-Side Out-of-Bounds Read Leading to Wild-Pointer Write via object_id

CVE-2026-71256 - nanoMODBUS Client-Side Out-of-Bounds Read Leading to Wild-Pointer Write via object_id

https://cvefeed.io/rssfeed/latest.atom / Wed, 08/05/2026 - 16:09
CVE ID :CVE-2026-71256
Published : Aug. 5, 2026, 12:18 p.m. | 36 minutes ago
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.
Severity: 9.8 | CRITICAL
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