---
id: "CVE-2026-98476"
kind: "vulnerability"
aliases: ["CVE-2026-98476"]
title: "Linux kernel s390 channel I/O: NULL pointer dereference crashes the system"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["ibm-z", "infrastructure", "linux-kernel", "mainframe", "s390"]
not_affected_if: ["non-s390-architecture"]
published_at: "2026-10-18T16:16:58+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:25:57+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98476", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel s390 channel I/O: NULL pointer dereference crashes the system

On IBM Z (s390) systems, a channel path entry can be removed while a subchannel still refers to it, and ccw_device_get_util_str() then dereferences a NULL pointer. The sources describe a kernel crash (NULL pointer dereference) and do not state any code execution or data exposure.

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

## How to check

- unknown

## Fix

- Update to a Linux kernel release that includes the upstream fix adding the NULL check in ccw_device_get_util_str() (fixed version not named in the sources)

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98476

## From the sources

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

s390/cio: Fix NULL pointer dereference in ccw_device_get_util_str()

The channel path registry entry associated with a CHPID may be removed
while the subchannel's PMCW still references that CHPID. In this case,
chpid_to_chp() can return NULL, leading to a NULL pointer dereference.

Add the missing NULL check before dereferencing the returned pointer.

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