{"cve":"CVE-2026-10647","nvd":{"published":"2026-06-29T22:16:42.940","modified":"2026-10-25T21:10:00.770","status":"Modified","description":"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).\n\nThe 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.\n\nThe 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.\n\nThe 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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","score":5.3},"cwes":["CWE-667","CWE-833"],"references":["https://github.com/zephyrproject-rtos/zephyr/commit/255bccc1badd1aa06c6e5ddf5b40de8463b33f02","https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-xcf7-r86m-5q9f"],"products":["zephyrproject:zephyr"],"source":"nvd","synced_at":"2026-10-25T23:44:33.281319194+00:00"},"epss":{"cve":"CVE-2026-10647","score":0.00201,"percentile":0.09868,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}