---
id: CVE-2026-10656
title: >-
  NULL-pointer dereference DoS in MAX32 USB device controller
  transfer-completion handlers
summary: >-
  The MAX32xxx USB device controller driver (drivers/usb/udc/udc_max32.c,
  compatible adi_max32_usbhs) dereferenced an endpoint buffer in its OUT and IN
  transfer-completion handlers without checking it for NULL.
  udc_event_xfer_out_done() ca…
severity: medium
cvss: 4.6
cvssVector: 'CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-476
vendor: zephyrproject
product: zephyr
affected:
  - zephyr >= 4.2.0 < 4.4.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-07-06T18:52:25.573518Z'
published: '2026-07-05'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:10:09.309Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-10656'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/a0d8f786559355fb3b38e34799e1ae491ba9545c
    label: Fix commit
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-58p9-6mjq-rf2m
    label: GHSA-58p9-6mjq-rf2m
tags:
  - cve.org
epss: 0.00281
epssPercentile: 0.19176
ingestedAt: '2026-10-15T22:48:25.566Z'
---

## Overview

The MAX32xxx USB device controller driver (drivers/usb/udc/udc_max32.c, compatible adi_max32_usbhs) dereferenced an endpoint buffer in its OUT and IN transfer-completion handlers without checking it for NULL. udc_event_xfer_out_done() called net_buf_add(buf, ep_request->actlen) immediately after buf = udc_buf_get(ep_cfg), where udc_buf_get() returns NULL when the endpoint FIFO is empty.

A transfer-completion event is queued from interrupt context and processed asynchronously by the driver thread; between queuing and processing, the endpoint FIFO can be drained by host-controlled control flow — in particular udc_setup_received() drains the EP0 OUT/IN FIFOs whenever a new SETUP packet arrives, and dequeue/disable/purge paths drain it likewise.

A USB host that aborts an in-flight EP0 control transfer with a new SETUP packet (legal USB behavior) can therefore cause a stale XFER_OUT_DONE event to be processed against an empty FIFO, producing net_buf_add(NULL, ...), a near-NULL pointer dereference that faults and crashes the device. No authentication is required; the attacker is the USB host the device is connected to (physical bus access). Impact is denial of service (device crash).

The defect was introduced when the MAX32 UDC driver was added and shipped in Zephyr v4.4.0. The fix adds NULL-buffer checks that return early with UDC_EVT_ERROR/-ENOBUFS in both the OUT-done and IN-done handlers.

## Affected

- `zephyr >= 4.2.0 < 4.4.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.