CVE-2026-29972

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.

Is your site exposed to CVE-2026-29972?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

8.2

HIGH

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

EPSS — Exploit Prediction

0.0007

Probability of exploitation

0.21%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-121 CWE-121

References

Other References

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

Frequently Asked Questions

What is CVE-2026-29972? +

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. It has a CVSS v3.1 base score of 8.2 (HIGH).

How severe is CVE-2026-29972? +

CVE-2026-29972 has a CVSS v3.1 score of 8.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0007, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-29972? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-6239

A stack‑based buffer overflow vulnerability exists in Tapo C520WS v2 in the ONVIF CreateUsers service, where the device fails to …

CVE-2026-8356

LibreOffice can import presentations in the legacy binary PPT format. A stack buffer overflow existed when importing a colour-replacement record. …

CVE-2026-40489

editorconfig-core-c is an EditorConfig core library for use by plugins supporting EditorConfig parsing. Versions up to and including 0.12.10 have …

CVE-2025-26382

Under certain circumstances the iSTAR Configuration Utility (ICU) tool could have a buffer overflow issue

CVE-2025-1533

A stack buffer overflow has been identified in the AsIO3.sys driver. This vulnerability can be triggered by input manipulation, may …

CVE-2025-3916

CWE-121: Stack-based Buffer Overflow vulnerability exists that could cause local attackers being able to exploit these issues to potentially execute …