# CVE-2026-10668: Zephyr OS Nuvoton NuMaker HSUSBD denial of service in USB driver

Source: https://junglewise.ai/threats/cve-2026-10668-zephyr-os-nuvoton-numaker-hsusbd-denial-of-service-in-usb-driver  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-12. Updated: 2026-07-12  
License: CC BY 4.0 with a link back

CVE-2026-10668 · Severity: low · CVSS 2.4 · Published 2026-07-12

A vulnerability in the Nuvoton NuMaker USB driver for Zephyr OS can allow a connected USB host to disable the device's USB functionality. By sending specific malformed or timed-out sequences, an attacker with physical access can cause the device to stop responding to all USB commands. This results in a denial of service that typically requires a physical unplug or device reset to recover.

Technologies: [Zephyr Project Zephyr OS](https://junglewise.ai/threats/technologies/zephyr-os). Vendors: [Zephyr Project](https://junglewise.ai/threats/vendors/zephyr-project).

## Quick answers

**Is CVE-2026-10668 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-10668 being exploited in the wild.

**How severe is CVE-2026-10668?** Low severity, with a CVSS score of 2.4, published 12 July 2026.

**Which products and versions are affected?** Zephyr Project Zephyr OS >= 4.4.0, < 4.5.0.

**Is there a fix for CVE-2026-10668?** A patch was published on 2026-05-13: Fix merged into main branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-10668 attacked?** It is attacked with physical access, in an operating system.

**Am I affected by CVE-2026-10668?** Check whether you run Zephyr Project Zephyr OS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The Nuvoton NuMaker HSUSBD USB device-controller driver (drivers/usb/udc/udc_numaker.c) unconditionally arms the control Data IN stage. Because the underlying hardware cannot disarm a previously armed Data IN transfer, a host that cancels an in-flight transfer and immediately issues a new SETUP packet causes a synchronization failure. This results in the control endpoint permanently NAK'ing subsequent transfers, leading to a denial of service. The vulnerability is limited to availability; memory safety is maintained as FIFO copy loops remain bounded by buffer lengths. The fix introduces event monitoring to ensure Data IN is only armed when an IN token is present and no new SETUP has arrived.

## Affected products

- Zephyr Project Zephyr OS >= 4.4.0, < 4.5.0

## Timeline

- 2026-07-12: disclosed
- 2026-07-12: advisory
- 2026-05-13: patched: Fix merged into main branch

## References

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

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