zephyrproject zephyr up to 4.4.x Exported Network Interface usbd_cdc_ncm.c usbd_ep_enqueue deadlock

Summaryinfo

A vulnerability, which was classified as problematic, was found in zephyrproject zephyr up to 4.4.x. This affects the function usbd_ep_enqueue of the file subsys/usb/device_next/class/usbd_cdc_ncm.c of the component Exported Network Interface. The manipulation results in deadlock. This vulnerability is reported as CVE-2026-10647. The attack can be launched remotely. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in zephyrproject zephyr up to 4.4.x. It has been classified as problematic. Affected is the function usbd_ep_enqueue of the file subsys/usb/device_next/class/usbd_cdc_ncm.c of the component Exported Network Interface. The manipulation with an unknown input leads to a deadlock vulnerability. CWE is classifying the issue as CWE-833. The product contains multiple threads or executable segments that are waiting for each other to release a necessary lock, resulting in deadlock. This is going to have an impact on availability. CVE summarizes:

The USB CDC-NCM device class (subsys/usb/device_next/class/usbd_cdc_ncm.c) ignores the return value of usbd_ep_enqueue() in its ethernet transmit callback cdc_ncm_send(). When the enqueue fails, the function still calls k_sem_take(&data-sync_sem, K_FOREVER), blocking on a completion semaphore that is only ever signaled from the bulk-IN transfer-completion callback. Because nothing was enqueued, that callback never fires and the calling thread — a shared network traffic-class TX thread — deadlocks permanently while holding the interface TX lock, halting transmission until reboot (and leaking the transmit buffer). The enqueue fails under conditions controlled by the attached USB host: usbd_ep_enqueue() returns -EPERM whenever the bus is suspended (a standard, persistent host operation), and the underlying udc_ep_enqueue() returns -EPERM/-ENODEV on disconnect, bus reset, or endpoint disable. The cdc_ncm_send() guard only checks the DATA_IFACE_ENABLED and IFACE_UP flags, not the suspended state, so a packet transmitted while the host holds the bus suspended reaches the failing enqueue and deadlocks the TX path. The realistic trigger is a bus suspend that occurs while the exported network interface is active and has traffic to send — host sleep, USB selective/auto-suspend, or hub power management — after which any device-originated packet deadlocks the path, recoverable only by reboot. The impact is a persistent loss of the virtual network connection between the host's NCM interface and the Zephyr device; because the deadlocked thread is a shared traffic-class TX thread, egress on other network interfaces can stall as well. There is no memory corruption or information disclosure. The defect was introduced with the CDC-NCM driver and shipped in releases through v4.4.0; it is fixed by checking the usbd_ep_enqueue() return value and freeing the buffer before the blocking wait.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-10647 since 06/02/2026. The exploitability is told to be difficult. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 4.5.0 eliminates this vulnerability. Applying the patch 255bccc1badd1aa06c6e5ddf5b40de8463b33f02 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-40235). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

• Project Management Software

Vendor

• zephyrproject

Name

• zephyr

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4

License

• open-source

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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