CVE-2026-10668: Host-triggerable control-endpoint wedge (DoS) in Nuvoton NuMaker HSUSBD UDC driver
The Nuvoton NuMaker HSUSBD USB device-controller driver (drivers/usb/udc/udcnumaker.c) armed the control Data IN stage unconditionally (base->CEPTXCNT = len in numakerhsusbdeptrigger). 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 netbuf length and the hardware BUFFULL flag) and the netbuf 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 (kevent) 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 (CONFIGUDCNUMAKER with DTHASNUVOTONNUMAKERHSUSBDENABLED); shipped in v4.4.0.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Apply the driver logic change in drivers/usb/udc/udc_numaker.c so that control Data IN is not armed unconditionally in numaker_hsusbd_ep_trigger; instead, monitor the IN-token and new-SETUP events and arm CEPTX only when IN token is present and no new SETUP has arrived, cancelling the current transfer on new SETUP to prevent the control-endpoint wedge/DoS.
Nuvoton NuMaker HSUSBD USB device-controller driver (CONFIG_UDC_NUMAKER / DT_HAS_NUVOTON_NUMAKER_HSUSBD_ENABLED) arm condition for control Data IN stage (base->CEPTXCNT) in numaker_hsusbd_ep_trigger = Arm only when an IN token is present and no new SETUP has arrived; on new SETUP cancel the current transfer (k_event)
Event History
Frequently Asked Questions
What is the severity of CVE-2026-10668?
CVE-2026-10668 has a low severity rating of 2.4.
What type of vulnerability is associated with CVE-2026-10668?
CVE-2026-10668 is classified as a DoS (Denial of Service) vulnerability.
How do I fix CVE-2026-10668?
To mitigate CVE-2026-10668, update the Nuvoton NuMaker HSUSBD USB device-controller driver to the latest version that addresses this issue.
What impact does CVE-2026-10668 have on systems?
CVE-2026-10668 can lead to a denial of service, causing the USB host to become unresponsive.
In which software is CVE-2026-10668 found?
CVE-2026-10668 is found in the Nuvoton NuMaker HSUSBD USB device-controller driver.