---
id: CVE-2026-98736
title: 'Bluetooth: hci_conn: Lock parent access during enhanced SCO setup'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  Bluetooth: hci_conn: Lock parent access during enhanced SCO setup

  Bluetooth: hci_conn: Lock parent access during enhanced SCO setup

  hci_enhanced_setup_sync() runs on …
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= e07a06b4eb417f5271d33ce2240e93c62d98b7b4 <
    1239ef0fa809b5952fca679db3faa3e1c00e1dac
  - >-
    Linux >= e07a06b4eb417f5271d33ce2240e93c62d98b7b4 <
    cabd58d9bb66d49d481f762ce986173db397435d
  - >-
    Linux >= e07a06b4eb417f5271d33ce2240e93c62d98b7b4 <
    93a737e4e042f59673cd580d35214f278d7b757d
  - >-
    Linux >= e07a06b4eb417f5271d33ce2240e93c62d98b7b4 <
    024e05f73a4c1263d031614bc36700ec135eecb4
  - Linux 6.1
published: '2026-10-18'
updated: '2026-10-18'
sourceUpdated: '2026-10-18T15:47:14.076Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-98736'
references:
  - url: 'https://git.kernel.org/stable/c/1239ef0fa809b5952fca679db3faa3e1c00e1dac'
  - url: 'https://git.kernel.org/stable/c/cabd58d9bb66d49d481f762ce986173db397435d'
  - url: 'https://git.kernel.org/stable/c/93a737e4e042f59673cd580d35214f278d7b757d'
  - url: 'https://git.kernel.org/stable/c/024e05f73a4c1263d031614bc36700ec135eecb4'
tags:
  - cve.org
ingestedAt: '2026-10-18T16:47:32.504Z'
---

## Overview

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

Bluetooth: hci_conn: Lock parent access during enhanced SCO setup

Bluetooth: hci_conn: Lock parent access during enhanced SCO setup

hci_enhanced_setup_sync() runs on the request workqueue without the
hci_dev_lock held by its caller when setup was queued. Its CVSD
capability check and find_next_esco_param() dereference conn->parent
while the receive workqueue can unlink and release that parent.

The following interleaving can cause a use-after-free:

  hci_enhanced_setup_sync()       hci_disconn_complete_evt()
  load conn->parent
                                 hci_dev_lock()
                                 hci_conn_del(ACL parent)
                                   unlink SCO child
                                   drop link's parent reference
                                   clear child->parent
                                   release ACL parent
                                     bt_link_release()
                                       kfree(parent)
                                 hci_dev_unlock()
  read parent->features[0][3]

The reference held for the queued SCO child does not keep its ACL parent
alive after unlinking. Commit 42de40abe25d ("Bluetooth: hci_conn: fix the
SCO setup context lifetime") protects the child stored in the queued
context, but leaves these parent accesses unprotected.

With a 40 ms diagnostic delay after loading conn->parent, an instrumented
kernel based on fd179f8a05be, which already contains 42de40abe25d,

  BUG: KASAN: slab-use-after-free in hci_enhanced_setup_sync+0xda5/0xdf0
  Read of size 1 at addr ffff888102204047 by task kworker/u17:0/93
  Call Trace:
   hci_enhanced_setup_sync+0xda5/0xdf0
   hci_cmd_sync_work+0x13c/0x290
   process_one_work+0x6b4/0x10e0

  Allocated by task 92:
   __hci_conn_add+0x304/0x1df0
   hci_connect_acl+0x349/0x3e0
   hci_connect_sco+0x3b/0x9a0
   sco_sock_connect+0x475/0xca0

  Freed by task 94:
   kfree+0x121/0x3c0
   bt_link_release+0x79/0xa0
   device_release+0xc8/0x240
   kobject_put+0x14d/0x280
   hci_conn_del+0x524/0xe30
   hci_disconn_complete_evt+0x403/0x8c0
   hci_event_packet+0x71b/0xb20
   hci_rx_work+0x293/0x730

The accessed address is 71 bytes into the freed ACL parent, at its
features[0][3] byte; the queued SCO child is a different object. The
diagnostic preserves the loaded parent across the delay, matching the
unmodified compiled capability check, and does not change the parent
references or teardown path.

Hold hci_dev_lock() across the codec switch, including every call to
find_next_esco_param(), and release it on all selection errors. Keep
configure_datapath_sync() outside the critical section because it waits
for HCI events. Preserve parameter selection and existing return values.

## Affected

- `Linux >= e07a06b4eb417f5271d33ce2240e93c62d98b7b4 < 1239ef0fa809b5952fca679db3faa3e1c00e1dac`
- `Linux >= e07a06b4eb417f5271d33ce2240e93c62d98b7b4 < cabd58d9bb66d49d481f762ce986173db397435d`
- `Linux >= e07a06b4eb417f5271d33ce2240e93c62d98b7b4 < 93a737e4e042f59673cd580d35214f278d7b757d`
- `Linux >= e07a06b4eb417f5271d33ce2240e93c62d98b7b4 < 024e05f73a4c1263d031614bc36700ec135eecb4`
- `Linux 6.1`

## Remediation

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