---
id: CVE-2026-10685
title: >-
  The Zephyr Bluetooth GATT client CCC-write response handler
  gatt_write_ccc_rsp() in subsys/bluetooth/host/gatt.c invoked the application's
  params->subscribe() callback after it had already called params->notify(conn,
  params, NULL, 0).


  P…
summary: >-
  The Zephyr Bluetooth GATT client CCC-write response handler
  gatt_write_ccc_rsp() in subsys/bluetooth/host/gatt.c invoked the application's
  params->subscribe() callback after it had already called params->notify(conn,
  params, NULL, 0).


  P…
severity: high
cvss: 7.6
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H'
cwe:
  - CWE-416
vendor: zephyrproject
product: zephyr
affected:
  - 'zephyr >= 2.4.0, < 4.5.0'
patched:
  - zephyr 4.5.0
published: '2026-07-31'
updated: '2026-08-07'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-10685'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/c7292f20223637232b6f962141725611a38f6a52
    label: vulnerabilities@zephyrproject.org
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-29xh-jm2m-4qvx
    label: vulnerabilities@zephyrproject.org
tags:
  - nvd
epss: 0.00304
epssPercentile: 0.20658
ingestedAt: '2026-08-08T15:23:02.487Z'
---

## Overview

The Zephyr Bluetooth GATT client CCC-write response handler gatt_write_ccc_rsp() in subsys/bluetooth/host/gatt.c invoked the application's params->subscribe() callback after it had already called params->notify(conn, params, NULL, 0).

Per the public GATT API, a notify callback with NULL data is the documented signal that the subscription has terminated and the bt_gatt_subscribe_params struct may be freed or reused by the application; calling subscribe() on the struct afterwards is a use-after-free, including an indirect call through the freed params->subscribe function pointer.

The error branch is remotely (adjacent) reachable: a Zephyr device acting as a GATT client that calls bt_gatt_subscribe() can be driven into this ordering when a connected GATT server peer answers the CCC write with an ATT Error Response (the peer-supplied error code flows through att_error_rsp -> att_handle_rsp into gatt_write_ccc_rsp).

For applications that free or recycle subscription parameters in their notification-termination handler, this results in memory corruption, a crash (denial of service), or potentially attacker-influenced control flow. The fix reorders the handler so the subscribe() callback runs before the terminating notify(NULL) in both the error and unsubscribe paths.

## Affected

- `zephyr >= 2.4.0, < 4.5.0`

## Remediation

Upgrade past the affected range:

- `zephyr 4.5.0`