---
id: "CVE-2026-98687"
kind: "vulnerability"
aliases: ["CVE-2026-98687"]
title: "Linux kernel: oversized Thunderbolt XDomain response causes heap out-of-bounds read"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["kernel", "linux", "runtime", "self-hosted", "thunderbolt"]
not_affected_if: ["driver-not-loaded", "no-thunderbolt-ports"]
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-2026-98687", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel: oversized Thunderbolt XDomain response causes heap out-of-bounds read

The Linux kernel Thunderbolt driver trusts a six-bit length field in XDomain property responses, so a malicious peer can make it copy 12 bytes past a heap buffer. The result is a heap out-of-bounds read that can leak kernel memory.

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

## How to check

- Check the running kernel version with `uname -r` and compare it with the fixed release in the NVD entry.
- Check whether the Thunderbolt driver is loaded with `lsmod | grep thunderbolt`.

## Fix

- Update the Linux kernel to a release that includes the upstream fix that rejects oversized XDomain properties responses (commit 322e93448d90 and follow-up 4db2bd2ed478 are the related history; the fixed release is unknown from the sources).

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98687

## From the sources

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

thunderbolt: Reject oversized XDomain properties responses

tb_xdp_properties_request() allocates room for 45 data dwords in its
252-byte response buffer.  The XDomain length field is six bits wide,
however, and a malicious peer can set it to 63.  After the fixed response
fields are subtracted, the driver treats this as 48 data dwords.

Commit 322e93448d90 ("thunderbolt: Clamp XDomain response data copy to
allocation size") only bounds the copy against data_len.  If data_len is
at least 48, memcpy() reads 192 bytes from the 180-byte res->data array,
causing a 12-byte heap out-of-bounds read.  Commit 4db2bd2ed478
("thunderbolt: Limit XDomain response copy to actual frame size") limits
the earlier copy but does not constrain this header-derived length.

Reject response data lengths that exceed the allocated source buffer
before copying them into the assembled property block.

---

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