---
title: "CVE-2026-79976: MCTP - Denial of Service"
description: "The MCTP-over-I2C+GPIO target binding in subsys/pmci/mctp/mctp_i2c_gpio_target.c contains a denial of service caused by stale register and data-phase flags not being cleared on I2C STOP, letting any controller on the bus cause device reset or halt, exploit requires controller access on the shared management bus."
url: https://panop.io/threat-heartbeat/CVE-2026-79976/
---

# CVE-2026-79976 MCTP - Denial of Service

The MCTP-over-I2C+GPIO target binding in subsys/pmci/mctp/mctp\_i2c\_gpio\_target.c contains a denial of service caused by stale register and data-phase flags not being cleared on I2C STOP, letting any controller on the bus cause device reset or halt, exploit requires controller access on the shared management bus.

CVSS base score 7.1 /10

High

CISA KEV

Not listed

Public exploit

None known

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-79976)

## Details

Type

Denial of Service

Impact

Denial Of Service

CVSS vector

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

Published

21 October 2026

Updated

22 October 2026

Weakness

[CWE-476](https://cwe.mitre.org/data/definitions/476.html)

## Vendor fix

Update to a version where b->reg\_addr and b->rxtx are reset at every I2C STOP, or apply the patch that clears these flags.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-79976](https://nvd.nist.gov/vuln/detail/CVE-2026-79976)
- [https://github.com/zephyrproject-rtos/zephyr/commit/60f7fee438504de29f2473d7a8d0535235b983ef](https://github.com/zephyrproject-rtos/zephyr/commit/60f7fee438504de29f2473d7a8d0535235b983ef)
- [https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-76fx-m4mf-24gq](https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-76fx-m4mf-24gq)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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