# CVE-2026-10656: NULL-pointer dereference DoS in MAX32 USB device controller transfer-completion handlers

Status: published. Published: 2026-07-05. Updated: 2026-11-04.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: zephyr) — https://github.com/zephyrproject-rtos/zephyr/commit/a0d8f786559355fb3b38e34799e1ae491ba9545c

## Affected products and versions

- zephyrproject / zephyr (zephyr): ≥ 4.2.0; < 4.4.1 (affected, semver). Source: CNA: zephyr

## Severity and prioritization

- CVSS 3.1: 4.6 (medium); CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: zephyr

- CISA KEV: No listing in collected sources

- EPSS: 0.28% as of 2026-11-03; percentile 20.69%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-476

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/a0d8f786559355fb3b38e34799e1ae491ba9545c (CNA: zephyr; patch)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-58p9-6mjq-rf2m (CNA: zephyr)

## Provenance

- CNA: zephyr: https://www.cve.org/CVERecord?id=CVE-2026-10656; retrieved 2026-11-04; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-10656; retrieved 2026-11-04; source updated Not reported

Revision: a99a7f1e4a192781184a5d2efa6c03ff35eca2612152dad75d19957b6485eb56

Canonical: https://y2.dev/cve/CVE-2026-10656

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