# CVE-2026-11893

## Summary

- **CVE ID:** CVE-2026-11893
- **Severity:** MEDIUM
- **CVSS Score:** 5.9 (CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H)
- **CWE:** CWE-415
- **Published:** Aug 11, 2026
- **Last Modified:** Aug 11, 2026

## 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.

## Affected Products

- zephyrproject — zephyr (4.4.0)

## References

- [CNA](https://github.com/zephyrproject-rtos/zephyr/commit/76d92d502b30218aaf11cbbe1be180a317627bb9)
- [CNA](https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-ph42-6rqx-728c)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.16%
- **EPSS Percentile:** 5.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._