Description
The Bluetooth HCI driver for Bouffalo Lab on-chip BLE controllers (BL60x/BL70x/BL61x), bt_bflb_send() in drivers/bluetooth/hci/hci_bflb.c, violates the bt_hci_driver_api.send() buffer-ownership contract. That contract (documented at include/zephyr/drivers/bluetooth.h) requires the buffer reference to be consumed only on success; on error the caller still owns the reference and unrefs it. The driver instead routed all error paths through a shared label that unconditionally called net_buf_unref(buf) before returning the error code, consuming the buffer on failure as well.

When send() returns an error, the host TX path (send_buf() in subsys/bluetooth/host/conn.c) unrefs the same buffer again, believing it still owns it. This double-unref over-decrements the net_buf reference count. Because the buffer is a TX fragment whose destroy callback also decrements its still-queued parent buffer, the parent is freed prematurely while reachable on the connection TX queue, producing a use-after-free and corruption of the shared net_buf pool rather than a benign leak.

The error conditions are on the host-to-controller transmit path (controller send failure, or an unsupported H:4 packet type), so they are not driven directly by attacker-supplied radio bytes; a remote/adjacent peer can influence them only indirectly, e.g. by inducing controller TX failures under heavy link load. The consequence when reached is BLE-stack denial of service (crash / pool corruption) with possible further memory corruption, bounded to devices using one of these Bouffalo Lab on-chip controllers.
Published: 2026-08-11
Score: 5.9 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

A double free and use‑after‑free flaw exists in the Bouffalo Lab Bluetooth HCI driver for Zephyr, where an error in the send() path incorrectly unrefs a buffer that the caller still owns. This contract violation results in a double unref, prematurely freeing a parent buffer still queued for transmission and corrupting the shared net_buf pool. The effect is a denial of service on the device, potentially followed by memory corruption.

Affected Systems

The issue affects Zephyr OS builds that include the hci_bflb driver for Bouffalo Lab on‑chip BLE controllers (BL60x, BL70x, BL61x). No specific version ranges are provided, but the vulnerability is present in the codebase referenced by the commit from the Zephyr project repository.

Risk and Exploitability

The CVSS score of 5.9 indicates medium severity, and the EPSS score is not available. The vulnerability is not listed in CISA KEV, suggesting no widely known exploits. Exploitation is not directly initiated by attacker‑supplied radio data; instead, a malicious peer might induce controller transmission failures under heavy link load, which may trigger the error path. Once triggered, the flaw causes a crash or memory corruption, but the attack vector requires the device to execute the incomplete driver code, limiting exposure largely to devices using the affected Bouffalo Lab controllers.

Generated by OpenCVE AI on August 11, 2026 at 06:22 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Upgrade Zephyr to a release that incorporates the fix illustrated in commit 76d92d502b30218aaf11cbbe1be180a317627bb9.
  • If an OS update is not immediately feasible, configure or isolate the device to avoid conditions that would cause frequent controller transmission failures, such as limiting high‑traffic BLE link usage.
  • Continuously monitor the device for unexpected crashes or memory corruption incidents and maintain logs to detect potential exploitation attempts.

Generated by OpenCVE AI on August 11, 2026 at 06:22 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 05:15:00 +0000

Type Values Removed Values Added
Description The Bluetooth HCI driver for Bouffalo Lab on-chip BLE controllers (BL60x/BL70x/BL61x), bt_bflb_send() in drivers/bluetooth/hci/hci_bflb.c, violates the bt_hci_driver_api.send() buffer-ownership contract. That contract (documented at include/zephyr/drivers/bluetooth.h) requires the buffer reference to be consumed only on success; on error the caller still owns the reference and unrefs it. The driver instead routed all error paths through a shared label that unconditionally called net_buf_unref(buf) before returning the error code, consuming the buffer on failure as well. When send() returns an error, the host TX path (send_buf() in subsys/bluetooth/host/conn.c) unrefs the same buffer again, believing it still owns it. This double-unref over-decrements the net_buf reference count. Because the buffer is a TX fragment whose destroy callback also decrements its still-queued parent buffer, the parent is freed prematurely while reachable on the connection TX queue, producing a use-after-free and corruption of the shared net_buf pool rather than a benign leak. The error conditions are on the host-to-controller transmit path (controller send failure, or an unsupported H:4 packet type), so they are not driven directly by attacker-supplied radio bytes; a remote/adjacent peer can influence them only indirectly, e.g. by inducing controller TX failures under heavy link load. The consequence when reached is BLE-stack denial of service (crash / pool corruption) with possible further memory corruption, bounded to devices using one of these Bouffalo Lab on-chip controllers.
Title Double free / use-after-free in Bouffalo Lab HCI driver send() error paths (hci_bflb)
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: 2026-08-11T04:42:39.049Z

Reserved: 2026-06-10T15:13:51.139Z

Link: CVE-2026-11893

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