---
id: "CVE-2026-98733"
kind: "vulnerability"
aliases: ["CVE-2026-98733"]
title: "Linux kernel: Bluetooth ISO fragment queueing race causes use-after-free"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["bluetooth", "infrastructure", "linux-kernel", "self-hosted"]
not_affected_if: ["no-bluetooth-iso"]
published_at: "2026-10-18T16:17:26+00:00"
first_seen_at: "2026-10-23T21:57:16+00:00"
updated_at: "2026-10-25T05:17:12+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98733", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel: Bluetooth ISO fragment queueing race causes use-after-free

In the Linux kernel's Bluetooth stack, fragmented ISO packets were queued without holding the queue lock, so the transmit worker could dequeue and free a packet while insertion still wrote to it. The sources describe a use-after-free that a local process could trigger with concurrent sends, with possible queue corruption.

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

## How to check

- unknown

## Fix

- Install a Linux kernel release that includes the upstream commit 'Bluetooth: hci_core: Serialize fragmented ISO packet queueing'
- unknown

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98733

## From the sources

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

Bluetooth: hci_core: Serialize fragmented ISO packet queueing

The fragmented path in hci_queue_iso() calls __skb_queue_tail() without
holding conn->data_q.lock. The socket lock serializes senders, but the
transmit worker can concurrently remove packets from this queue using
skb_dequeue().

After an insertion saves the old tail pointer, hci_sched_iso() can dequeue
that packet and pass it to the driver. The driver can free the packet
before the insertion resumes and writes to the old tail's next pointer,
causing a use-after-free. Concurrent updates can also corrupt the queue.

KASAN reported:

  BUG: KASAN: slab-use-after-free in hci_send_iso+0xc7d/0xe10
  Call Trace:
   hci_send_iso+0xc7d/0xe10
   iso_sock_sendmsg+0x710/0x900
   __sys_sendto+0x34a/0x3a0

  Allocated by task 86:
   __alloc_skb+0xdd/0x820
   alloc_skb_with_frags+0x7e/0x770
   sock_alloc_send_pskb+0x67a/0x820
   bt_skb_sendmsg.constprop.0+0xc0/0x6c0
   iso_sock_sendmsg+0x44e/0x900

  Freed by task 90:
   kmem_cache_free+0xcb/0x3d0
   vhci_read+0x33f/0x4d0
   vfs_read+0x177/0xa20

Hold the queue lock across the entire fragment batch, as hci_queue_acl()
does, to serialize insertion against dequeue while preserving fragment
ordering.

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