---
id: "CVE-2026-98734"
kind: "vulnerability"
aliases: ["CVE-2026-98734"]
title: "Linux kernel: Bluetooth SCO and ISO scheduling can use freed connections"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["bluetooth", "linux-kernel", "runtime", "self-hosted"]
not_affected_if: ["bluetooth-not-loaded"]
published_at: "2026-10-18T16:17:27+00:00"
first_seen_at: "2026-10-23T21:57:16+00:00"
updated_at: "2026-10-25T05:17:11+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98734", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel: Bluetooth SCO and ISO scheduling can use freed connections

A race in the Linux kernel Bluetooth stack lets the transmit worker use a connection object after teardown has freed it, a use-after-free shown by KASAN. The sources do not state what an attacker can get beyond a kernel memory corruption crash or code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- `uname -r` to see the running kernel version
- `lsmod | grep -i bluetooth` to check whether the Bluetooth stack is loaded
- unknown for a fixed-version list, as the sources do not give one

## Fix

- Install the kernel release that carries the upstream fix for this CVE, from your distribution or kernel.org stable branch
- unknown for the exact fixed version, as the sources do not name it

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98734

## From the sources

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

Bluetooth: hci_core: Serialize SCO and ISO scheduling with teardown

hci_low_sent() selects a connection under RCU but drops the read lock
before calculating its quota and returning it to the scheduler. The
connection is then used without lifetime protection by hci_sched_iso()
and hci_sched_sco().

After the TX worker drops the RCU read lock, hci_abort_conn_sync() on
hdev->req_workqueue can remove the connection from the hash, complete
synchronize_rcu(), purge its queues and release it. The TX worker on
hdev->workqueue can then access the freed connection in hci_quote_sent()
or while dequeuing packets and updating conn->sent.

KASAN reported:

  BUG: KASAN: slab-use-after-free in hci_low_sent+0x730/0x840
  Workqueue: hci0 hci_tx_work
  Call Trace:
   hci_low_sent+0x730/0x840
   hci_sched_iso+0x25e/0x4d0
   hci_tx_work+0x239/0xcb0

  Allocated by task 93:
   __hci_conn_add+0x16f/0x1b40
   hci_bind_bis+0x782/0x17b0
   hci_connect_bis+0xa0/0x510
   iso_sock_connect+0x589/0x1050

  Freed by task 88:
   kfree+0x131/0x3c0
   device_release+0xc8/0x240
   kobject_put+0x14d/0x280
   hci_conn_del+0x55a/0xe80
   hci_disconnect_sync+0x156/0x180
   hci_abort_conn_sync+0x3e7/0x940
   hci_cmd_sync_work+0x13c/0x290

Hold hci_dev_lock() across connection selection and transmission in both
SCO and ISO scheduling, serializing them with connection teardown. This
also prevents queuing completion timestamps after the connection queues
have been purged. Extending RCU across transmission would be unsafe
because the transmit path can sleep. Keep the ISO timeout check outside
the mutex since hci_link_tx_to() takes it itself.

The preceding channel fix already holds this mutex in the ACL and LE
schedulers, which call the SCO scheduler between packets. Move the SCO
body to __hci_sched_sco(), assert that its caller holds the mutex, and
use it directly from these locked paths. Keep a locking hci_sched_sco()
wrapper for the direct calls from hci_tx_work(). This avoids recursively
acquiring the device mutex while preserving the scheduling order.

Remove the obsolete claim that connection removal disables TX.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_