Description
The Realtek BEE Bluetooth HCI driver's send callback, bt_hci_bee_send() in drivers/bluetooth/hci/hci_bee.c, violated the bt_hci_driver_api buffer-ownership contract. That contract requires the driver to consume (unref) the transmit net_buf only on success; on an error return the host caller retains ownership and unrefs the buffer itself. The pre-fix code routed all error paths through a shared cleanup label that unconditionally called net_buf_unref(buf) before returning the error code.

Because the host TX paths (in subsys/bluetooth/host/hci_core.c) unref the buffer again after send() returns an error, the buffer is freed twice: the driver returns it to its net_buf pool and the host then unrefs the already-freed buffer, corrupting the shared pool / underflowing the reference count (CWE-415). The same error branch additionally dereferenced buf->len inside a LOG_ERR call after the buffer had already been unref'd, a read of freed memory (CWE-416) that is compiled in at the default error log level.

The failing edges are reached when the controller's host-to-controller buffer allocation fails or the controller send fails (resource-exhaustion / IO conditions). A remote Bluetooth peer can push the device toward these conditions indirectly by driving heavy host transmit activity, at which point the double-free corrupts the host net_buf pool and most likely crashes the device, with residual potential for further memory corruption. The impact is confined to builds using this specific Realtek BEE HCI driver.

The fix returns early from each error path without unreffing and unrefs the buffer only on the success path, restoring the ownership contract and eliminating both the double-free and the use-after-free read.
Published: 2026-08-11
Score: 5.9 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

The Realtek BEE Bluetooth HCI driver violates the buffer‑ownership contract by unreferencing a transmit buffer on all error paths. The driver’s error handling drops the reference count even when the host caller retains ownership, leading to a double‑free. The same path also reads freed memory during an error log. These weaknesses match CWE‑415 (and CWE‑416). The result is corruption of the shared net‑buffer pool and a high likelihood of a crash or further memory corruption. The impact is limited to builds that include the specific Realtek BEE driver, but the crash can compromise device availability.

Affected Systems

Products affected are Zephyr Project: Zephyr builds that incorporate the Realtek BEE Bluetooth HCI driver. No specific version information is listed in the advisory; any build using that driver implementation before the security fix is vulnerable.

Risk and Exploitability

The CVSS score of 5.9 classifies the issue as medium severity. The EPSS score is not provided, and the vulnerability is not listed in the CISA KEV catalog. Attackers can induce the failure condition by venturing heavy host‑to‑controller activity from a remote Bluetooth peer, potentially exhausting controller buffer resources or triggering a send error. Upon reaching the failure edge, the double‑free corrupts the buffer pool, most likely leading to a device crash. The exploitable conditions are limited to remote traffic that stresses the Bluetooth stack; no local privileges are required.

Generated by OpenCVE AI on August 11, 2026 at 06:21 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Update Zephyr to a release that includes the commit restoring proper buffer‑ownership handling for the Realtek BEE HCI driver.
  • Rebuild the firmware with the updated driver to ensure the double‑free and use‑after‑free bugs are fixed.
  • If an immediate update is not available, disable non‑essential Bluetooth functionality until the patch is applied.

Generated by OpenCVE AI on August 11, 2026 at 06:21 UTC.

Tracking

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Advisories

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History

Tue, 11 Aug 2026 06:45:00 +0000

Type Values Removed Values Added
First Time appeared Zephyrproject
Zephyrproject zephyr
Vendors & Products Zephyrproject
Zephyrproject zephyr

Tue, 11 Aug 2026 05:45:00 +0000

Type Values Removed Values Added
Description The Realtek BEE Bluetooth HCI driver's send callback, bt_hci_bee_send() in drivers/bluetooth/hci/hci_bee.c, violated the bt_hci_driver_api buffer-ownership contract. That contract requires the driver to consume (unref) the transmit net_buf only on success; on an error return the host caller retains ownership and unrefs the buffer itself. The pre-fix code routed all error paths through a shared cleanup label that unconditionally called net_buf_unref(buf) before returning the error code. Because the host TX paths (in subsys/bluetooth/host/hci_core.c) unref the buffer again after send() returns an error, the buffer is freed twice: the driver returns it to its net_buf pool and the host then unrefs the already-freed buffer, corrupting the shared pool / underflowing the reference count (CWE-415). The same error branch additionally dereferenced buf->len inside a LOG_ERR call after the buffer had already been unref'd, a read of freed memory (CWE-416) that is compiled in at the default error log level. The failing edges are reached when the controller's host-to-controller buffer allocation fails or the controller send fails (resource-exhaustion / IO conditions). A remote Bluetooth peer can push the device toward these conditions indirectly by driving heavy host transmit activity, at which point the double-free corrupts the host net_buf pool and most likely crashes the device, with residual potential for further memory corruption. The impact is confined to builds using this specific Realtek BEE HCI driver. The fix returns early from each error path without unreffing and unrefs the buffer only on the success path, restoring the ownership contract and eliminating both the double-free and the use-after-free read.
Title Double-free / use-after-free in Realtek BEE Bluetooth HCI driver `send()` error paths
Weaknesses CWE-415
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H'}

Subscriptions

Zephyrproject Zephyr
cve-icon MITRE

Status: PUBLISHED

Assigner: zephyr

Published:

Updated: 2026-08-11T05:08:51.464Z

Reserved: 2026-06-10T15:25:18.616Z

Link: CVE-2026-11894

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-11T06:30:06Z

Weaknesses