# CVE-2026-11893: Double free / use-after-free in Bouffalo Lab HCI driver send() error paths (hci_bflb)

> A double free in the Bouffalo Lab Bluetooth HCI driver causes use-after-free, leading to denial of service or potential code execution on affected devices.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 Aug 2026
- **Updated:** 11 Aug 2026
- **Also known as:** GHSA-ph42-6rqx-728c

## What is CVE-2026-11893?

CVE-2026-11893 is a medium-severity use after free vulnerability in zephyrproject zephyr, published on 11 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2026-11893?


## How do I fix CVE-2026-11893?

No fix has been published for CVE-2026-11893 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-11893 being exploited?

There is no known exploitation of CVE-2026-11893 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-11893 and fix it if it is affected.

What it is: CVE-2026-11893 is a medium-severity use after free vulnerability in zephyrproject zephyr, published on 11 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-11893 in the wild and no public exploit code.

Affected product: zephyrproject zephyr. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-11893/ (Markdown: https://insights.sbomify.com/CVE-2026-11893/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-11893
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-11893
- OSV: https://osv.dev/vulnerability/CVE-2026-11893

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-11893/
Summaries are generated and may contain mistakes; the official description above is the record.