What’s Vulnerable › Vulnerabilities

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

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-05 · updated 2026-10-24
• Weakness: CWE-125

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].

Affected products

• debevv nanoMODBUS: through 1.23.0

References

• https://github.com/debevv/nanoMODBUS
• https://github.com/debevv/nanoMODBUS/blob/master/nanomodbus.c

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