CVE-2026-19940 zephyrproject CVE debrief

Who should care

Defenders of systems using Zephyr Project's Bluetooth Classic Hands-Free Profile Audio Gateway implementation should assess exposure and apply patches or mitigations to prevent potential system hangs or faults. This includes operators, platform administrators, vulnerability management teams, and security teams who need to review and apply patches or mitigations to prevent potential system hangs or faults.

Why it matters

CVE-2026-19940 is a denial of service vulnerability in the Bluetooth Classic Hands-Free Profile Audio Gateway implementation in Zephyr Project. Defenders of systems using this implementation should assess exposure and apply patches or mitigations to prevent potential system hangs or faults.

• Denial of service due to system hang or fault
• Verification of patch application and configuration changes required

Technical summary

The Bluetooth Classic Hands-Free Profile Audio Gateway implementation in subsys/bluetooth/host/classic/hfp_ag.c keeps its struct bt_hfp_ag objects in a static pool indexed by ACL connection index. On link teardown, hfp_ag_disconnected() cancels ag->tx_work and the per-call work items and then clears ag->acl_conn, which marks the pool slot as free — but it leaves ag->ongoing_call_work (and ag->slc_work) untouched.

Defensive priority

High

Recommended defensive actions

• Review and apply patches from the Zephyr Project
• Disable CONFIG_BT_HFP_AG if not required
• Implement asynchronous get_ongoing_call callback with timeout
• 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 Bluetooth Classic Hands-Free Profile Audio Gateway implementation in subsys/bluetooth/host/classic/hfp_ag.c has a vulnerability that can cause a denial of service. The vulnerability is caused by the improper handling of a k_work_delayable object, which can lead to corruption of the kernel's timeout list.

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.