CVE-2026-19741 zephyrproject CVE debrief

Who should care

Defenders responsible for Zephyr-based IoT devices, especially those using OpenThread integration, should assess exposure and prioritize verification and remediation. They should review and update build configurations to ensure a 6-to-32-character PSKd is configured and provision a per-device PSKd from factory data.

Why it matters

CVE-2026-19741 allows an unauthenticated attacker to control operational datasets in Zephyr's OpenThread integration, impacting IoT device security.

• An attacker can see, drop, inject, and spoof IPv6 traffic.
• An attacker can impersonate peers the application expects.
• A device is cut off from the network it was meant to join.
• Remediation requires verifying and updating vulnerable configurations.

Technical summary

The vulnerability is caused by a default PSKd of 'J01NME' being compiled into the firmware image when CONFIG_OPENTHREAD_JOINER_AUTOSTART=y and the PSKd is not overridden. An unauthenticated attacker within 802.15.4 radio range 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, allowing the attacker to see, drop, inject, and spoof IPv6 traffic and impersonate peers.

Defensive priority

Defenders should prioritize verifying and updating vulnerable configurations, especially for devices that enable joiner autostart and leave the PSKd unset.

Recommended defensive actions

• Verify and update vulnerable configurations, especially for devices that enable joiner autostart and leave the PSKd unset.
• Provision a per-device PSKd from factory data and call otJoinerStart() from the application.
• Review and update build configurations to ensure a 6-to-32-character PSKd is configured.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The vulnerability is caused by a default PSKd of 'J01NME' being compiled into the firmware image when CONFIG_OPENTHREAD_JOINER_AUTOSTART=y and the PSKd is not overridden. The PSKd is the only value that authenticates Thread commissioning. The fix removes the default from CONFIG_OPENTHREAD_JOINER_PSKD and adds a BUILD_ASSERT() 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

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.