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Vulnerability record · CVE-2026-29972 · published 8 May 2026

CVE-2026-29972: Stack-based buffer overflow vulnerability

nanoMODBUS through v1.22.0 has a stack-based buffer overflow in recv_read_registers_res() in nanomodbus.c. When a client calls nmbs_read_holding_registers() or nmbs_read_input_registers(), the library writes register data from the server response to the caller-provided buffer based on the response's byte_count field before validating that byte_count matches the requested quantity. A malicious Modbus TCP server can send a response with byte_count=250 (125 registers) regardless of the requested quantity, causing up to 248 bytes of attacker-controlled data to overflow the buffer, potentially allowing remote code execution.

8.2 CVSS 3.1 High EPSS 0.92% · top 41.2% CWE-121 · Stack-based buffer overflow Deferred
8.2CVSS 3.1 base score
0.92%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

Description

nanoMODBUS through v1.22.0 has a stack-based buffer overflow in recv_read_registers_res() in nanomodbus.c. When a client calls nmbs_read_holding_registers() or nmbs_read_input_registers(), the library writes register data from the server response to the caller-provided buffer based on the response's byte_count field before validating that byte_count matches the requested quantity. A malicious Modbus TCP server can send a response with byte_count=250 (125 registers) regardless of the requested quantity, causing up to 248 bytes of attacker-controlled data to overflow the buffer, potentially allowing remote code execution.

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

References

LinkTags
https://gist.github.com/dwilliams27/a4e26fe747c8561d608f7549804bd85f
https://github.com/debevv/nanoMODBUS
https://github.com/debevv/nanoMODBUS/blob/master/nanomodbus.c#L580-L615

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Source: NIST National Vulnerability Database (record CVE-2026-29972), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.