CVE-2026-10647: The USB CDC-NCM device class (subsys/usb/device_next/class/usbd_cdc_ncm.c) ignores the return value of usbd_ep

Q: How do I fix CVE-2026-10647?

zephyr: upgrade to 4.5.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-10647 being exploited?

CVE-2026-10647 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-10647 affect?

CVE-2026-10647 affects zephyr. Severity is medium (CVSS 5.3). 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->sy

Routine

MEDIUM 5.3UPGRADE

CVE-2026-10647 is a medium-severity flaw (CVSS 5.3) affecting zephyr. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 —

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Adjacent network
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 90%)
CISA exploited list	No
Weakness	CWE-833, CWE-667
Published	2026-06-29
Last modified	2026-10-25

Publisher (CNA): Zephyr Project · Vendor: zephyrproject

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-29 22:16 UTCPublished CVE record published
2026-10-25 21:10 UTCUpdated Record last modified

zephyrproject zephyr UPGRADE

Affected: >= 4.1.0 and < 4.5.0

Fixed in: 4.5.0

Safe to downgrade to: a release before 4.1.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-10647?

zephyr: upgrade to 4.5.0. Exact commands for each OS are on this page.

Is CVE-2026-10647 being exploited?

CVE-2026-10647 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-10647 affect?

CVE-2026-10647 affects zephyr. Severity is medium (CVSS 5.3). 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->sy

How urgent is CVE-2026-10647?

Priority 26/100. Public exploit reference

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References

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