---
id: "CVE-2026-98688"
kind: "vulnerability"
aliases: ["CVE-2026-98688"]
title: "Linux kernel: Thunderbolt race can dereference a NULL root switch pointer"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "laptops", "linux-kernel", "thunderbolt", "workstations"]
not_affected_if: ["no-thunderbolt-hardware"]
published_at: "2026-10-18T16:17:22+00:00"
first_seen_at: "2026-10-23T21:57:16+00:00"
updated_at: "2026-10-25T05:19:07+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98688", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel: Thunderbolt race can dereference a NULL root switch pointer

A race between the Thunderbolt removal work and domain teardown in the Linux kernel can dereference a NULL root switch pointer, causing a crash. The sources describe a kernel NULL dereference and do not state a code-execution or data-exposure impact.

_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
- Check whether the Thunderbolt driver is loaded with `lsmod | grep thunderbolt`
- Compare the running kernel against the fixed version in the kernel stable advisory, which the sources do not name

## Fix

- Install a Linux kernel build that contains the upstream commit that fixes tb_remove_work() by holding tb->lock and checking tb->root_switch; the exact fixed version is unknown from the sources
- Reboot into the patched kernel

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98688

## From the sources

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

thunderbolt: Fix NULL dereference in tb_remove_work()

There is a slight race between tb_remove_work() and tb_domain_remove()
which leads to dereferencing a NULL tb->root_switch pointer inside
tb_free_unplugged_xdomains():

        Thread A                            Thread B

  tb_remove_work()
                                    tb_domain_remove()
                                      mutex_lock(&tb->lock)
                                      tb_stop()
                                        /* doesn't cancel a running callback */
                                        cancel_delayed_work(&tcm->remove_work)
                                        ...
                                        tb_switch_remove(tb->root_switch)
                                        tb->root_switch = NULL
                                      mutex_unlock(&tb->lock)
    mutex_lock(&tb->lock)
    ...
    /* without checking ->root_switch */
    tb_free_unplugged_xdomains(tb->root_switch)
    mutex_unlock(&tb->lock)

Commit a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without
holding tb->lock") doesn't seem right to move tb_free_unplugged_xdomains()
out of the &tb->lock section and the check for tb->root_switch, in
particular.  It states:

  For this reason separate removing the XDomain from the topology data
  structures (where we need the lock) from unregistering the device from
  the bus (where remove callbacks of the drivers are being called).

tb_free_unplugged_xdomains() belongs to the former group of functions
requiring the lock.  And it also calls tb_xdomain_remove() which should
only be called with &tb->lock held.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

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