---
id: CVE-2026-99239
title: 'Bluetooth: L2CAP: refuse __l2cap_chan_add if chan already has conn'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  Bluetooth: L2CAP: refuse __l2cap_chan_add if chan already has conn

  l2cap_chan may be linked to l2cap_conn at most once. This is assumed in
  several places, eg l2cap_cha…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 8f90405a4a6f1f1880dc07996b47bf57c712bd8a <
    85cc289eb08afa975375f838187369e68b429ee0
  - >-
    Linux >= 32d783cafb46ff3ca58e6f9fd62c9c5f35eaf26b <
    820579652b24ce277e0097cd65b42bd9b7b8bf07
  - >-
    Linux >= 8922c7940bae9ce4b1736dddb6362370793835c2 <
    e618d928ec7f88cbeadfa3542adcac40f474e629
  - >-
    Linux >= 91047a4396a8b1857a6f712a90cf33ec0012b189 <
    fabaff1c59ff2cc89cb7e5bd0186a5e15f0c73b2
  - >-
    Linux >= 0b0e2bf39cf99e458d991b9df253727e036a7d7d <
    52fe88e4ef87311eee32b45c65603e7c69e75e7d
  - >-
    Linux >= d3b739db5dc6f688a60d56da872fabaf65246032 <
    10c705dd706aa93164ba41f2566f15206d6c178e
  - >-
    Linux >= b66774b48dd98f07254951f74ea6f513efe7ff8b <
    73820561d8cbfd3364a29b8fa77f1707f26029da
  - >-
    Linux >= b66774b48dd98f07254951f74ea6f513efe7ff8b <
    d3afd7803f9bc2a8c4270199497b60158b2fc647
  - >-
    Linux >= b66774b48dd98f07254951f74ea6f513efe7ff8b <
    86b55991d3cd690e73c5ef8d20b75ae4905b357a
  - Linux 50c38d9f42a529691e4e67ea9cedf4f0bfc8d277
  - Linux >= 5.10.265 < 5.10.273
  - Linux >= 5.15.216 < 5.15.224
  - Linux >= 6.1.183 < 6.1.191
  - Linux >= 6.6.145 < 6.6.161
  - Linux >= 6.12.97 < 6.12.115
  - Linux >= 6.18.39 < 6.18.60
  - Linux >= 7.1.4 < 7.2
  - Linux 7.2
published: '2026-11-02'
updated: '2026-11-03'
sourceUpdated: '2026-11-03T19:13:06.554Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-99239'
references:
  - url: 'https://git.kernel.org/stable/c/85cc289eb08afa975375f838187369e68b429ee0'
  - url: 'https://git.kernel.org/stable/c/820579652b24ce277e0097cd65b42bd9b7b8bf07'
  - url: 'https://git.kernel.org/stable/c/e618d928ec7f88cbeadfa3542adcac40f474e629'
  - url: 'https://git.kernel.org/stable/c/fabaff1c59ff2cc89cb7e5bd0186a5e15f0c73b2'
  - url: 'https://git.kernel.org/stable/c/52fe88e4ef87311eee32b45c65603e7c69e75e7d'
  - url: 'https://git.kernel.org/stable/c/10c705dd706aa93164ba41f2566f15206d6c178e'
  - url: 'https://git.kernel.org/stable/c/73820561d8cbfd3364a29b8fa77f1707f26029da'
  - url: 'https://git.kernel.org/stable/c/d3afd7803f9bc2a8c4270199497b60158b2fc647'
  - url: 'https://git.kernel.org/stable/c/86b55991d3cd690e73c5ef8d20b75ae4905b357a'
tags:
  - cve.org
epss: 0.00126
epssPercentile: 0.02302
ingestedAt: '2026-11-05T20:33:06.390Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: L2CAP: refuse __l2cap_chan_add if chan already has conn

l2cap_chan may be linked to l2cap_conn at most once. This is assumed in
several places, eg l2cap_chan_del cleanup.

There is a TOCTOU race where the invariant is violated:

    [Task 1]                          [Task 2]
    l2cap_chan_connect                l2cap_sock_bind
      l2cap_chan_lock                   lock_sock
      l2cap_state_change                if (sk->sk_state != BT_OPEN)
        chan->state = BT_CONNECT
        l2cap_sock_state_change_cb      chan->state = BT_BOUND
                                        sk->sk_state = BT_BOUND
          lock_sock <------------------ release_sock
          sk->sk_state = BT_CONNECT

l2cap_sock_connect() does not check sk->sk_state, so since chan->state
is now BT_BOUND, subsequent connect() ends up with second
__l2cap_chan_add.

Explicitly document and check the invariant in __l2cap_chan_add with
WARN_ON_ONCE. The only callsite where it could be hit is
l2cap_chan_connect, so add pre-check there to avoid relying on
chan->state. chan->state read/write is not properly guarded currently so
there can be other TOCTOUC problems.

Add l2cap_lock_chan in l2cap_sock_bind() to guard chan->state write.

## Affected

- `Linux >= 8f90405a4a6f1f1880dc07996b47bf57c712bd8a < 85cc289eb08afa975375f838187369e68b429ee0`
- `Linux >= 32d783cafb46ff3ca58e6f9fd62c9c5f35eaf26b < 820579652b24ce277e0097cd65b42bd9b7b8bf07`
- `Linux >= 8922c7940bae9ce4b1736dddb6362370793835c2 < e618d928ec7f88cbeadfa3542adcac40f474e629`
- `Linux >= 91047a4396a8b1857a6f712a90cf33ec0012b189 < fabaff1c59ff2cc89cb7e5bd0186a5e15f0c73b2`
- `Linux >= 0b0e2bf39cf99e458d991b9df253727e036a7d7d < 52fe88e4ef87311eee32b45c65603e7c69e75e7d`
- `Linux >= d3b739db5dc6f688a60d56da872fabaf65246032 < 10c705dd706aa93164ba41f2566f15206d6c178e`
- `Linux >= b66774b48dd98f07254951f74ea6f513efe7ff8b < 73820561d8cbfd3364a29b8fa77f1707f26029da`
- `Linux >= b66774b48dd98f07254951f74ea6f513efe7ff8b < d3afd7803f9bc2a8c4270199497b60158b2fc647`
- `Linux >= b66774b48dd98f07254951f74ea6f513efe7ff8b < 86b55991d3cd690e73c5ef8d20b75ae4905b357a`
- `Linux 50c38d9f42a529691e4e67ea9cedf4f0bfc8d277`
- `Linux >= 5.10.265 < 5.10.273`
- `Linux >= 5.15.216 < 5.15.224`
- `Linux >= 6.1.183 < 6.1.191`
- `Linux >= 6.6.145 < 6.6.161`
- `Linux >= 6.12.97 < 6.12.115`
- `Linux >= 6.18.39 < 6.18.60`
- `Linux >= 7.1.4 < 7.2`
- `Linux 7.2`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.