CVE-2026-19741

What it is

Zephyr's OpenThread integration defined CONFIG_OPENTHREAD_JOINER_PSKD with default "J01NME" in modules/openthread/Kconfig.thread (previously subsys/net/l2/openthread/Kconfig, then subsys/net/l2/openthread/Kconfig.thread). J01NME is the example Joining Device Credential used throughout the public OpenThread and Thread commissioning documentation, including Zephyr's own samples/net/sockets/echo_client/README.rst, so it is not a secret. A firmware image built with CONFIG_OPENTHREAD_JOINER_AUTOSTART=y that never overrode the PSKd therefore shipped with a publicly known joining credential compiled in, with no build-time or run-time warning. The PSKd is the only value that authenticates Thread commissioning: joiner and commissioner run a DTLS-PSK handshake keyed on it, after which the commissioner supplies the full operational dataset. In ot_configure_instance() (modules/openthread/openthread.c), a device with no stored dataset calls otJoinerStart() with the configured PSKd, and ot_joiner_start_handler() calls otThreadSetEnabled() on success. An unauthenticated attacker within 802.15.4 radio range of an uncommissioned device (factory-fresh, after a factory reset, or after a settings erase) can run any stock Thread commissioner registered with J01NME, complete the handshake, and hand the device an attacker-controlled operational dataset. The device then joins and enables Thread on the attacker's mesh. The attacker becomes its router, seeing, dropping, injecting and spoofing all of the device's IPv6 traffic and impersonating the peers the application expects, while the device is cut off from the network it was meant to join and stays mis-provisioned until it is reset. Only application-layer security with independently provisioned credentials survives. Exposure is limited to builds that enable joiner autostart and leave the PSKd unset; the option is not enabled by default and no in-tree sample uses the vulnerable combination. The fix removes the default from CONFIG_OPENTHREAD_JOINER_PSKD and adds a BUILD_ASSERT() in modules/openthread/openthread.c, active only under CONFIG_OPENTHREAD_JOINER_AUTOSTART, that fails the build unless a 6-to-32-character PSKd is configured. Products should provision a per-device PSKd from factory data and call otJoinerStart() from the application rather than relying on a credential compiled identically into every unit.

At a glance

Exploitability

Can be exploited from the same network segment without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-13 13:46 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-10-23 20:17 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-11-04 05:18 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.3% in the next 30 days (EPSS).
• Severity: 7.5 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-10-23 20:17 UTC

Last modified

2026-11-04 05:18 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-1392

Record status

Awaiting Analysis

Attack profile CVSS 3.1 · 7.5

Attack vector

Adjacent network

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-19741.md and follow it. Check whether this project is affected by CVE-2026-19741. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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