CVE-2026-77684: Zephyr Bluetooth Classic Hands-Free Profile buffer leak

CVE-2026-77684 · Severity: medium · CVSS 5.7 · Published 2026-10-19

Zephyr's Bluetooth Hands-Free Profile implementation leaks command buffers when connections disconnect, exhausting a fixed pool after repeated connect/disconnect cycles. An attacker with an established HFP session can trigger this leak remotely, and when the buffer pool is exhausted, the Bluetooth receive thread hangs indefinitely, blocking all HCI event processing and requiring a device reboot.

Technologies: Zephyr RTOS. Vendors: Zephyr.

Quick answers

Is CVE-2026-77684 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-77684 being exploited in the wild.
How severe is CVE-2026-77684?
Medium severity, with a CVSS score of 5.7, published 19 October 2026.
Which products and versions are affected?
Zephyr RTOS with CONFIG_BT_HFP_HF enabled.
Is there a fix for CVE-2026-77684?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-77684 attacked?
It is attacked over the network, in an operating system.
Am I affected by CVE-2026-77684?
Check whether you run Zephyr RTOS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The hfp_hf_disconnected() function fails to dequeue pending AT command buffers from hf->tx_pending when the RFCOMM DLC closes, and hfp_hf_create() unconditionally memsets the HF object without checking if work items are still scheduled, corrupting kernel workqueue state. A remote Audio Gateway peer can repeatedly trigger codec selection exchanges followed by immediate disconnection, starving the fixed hf_pool (CONFIG_BT_MAX_CONN + 1 buffers) and causing subsequent HFP sends to block forever in the Bluetooth RX context with K_FOREVER timeout semantics, halting all HCI event processing.

Affected products

  • Zephyr Zephyr RTOS with CONFIG_BT_HFP_HF enabled

Timeline

  • 2026-10-19: disclosed

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