---
id: "CVE-2026-98475"
kind: "vulnerability"
aliases: ["CVE-2026-98475"]
title: "Linux kernel s390: channel measurement block uses wrong address type"
severity: "low"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["ibm-z", "infrastructure", "linux-kernel", "s390"]
not_affected_if: ["kernel-without-randomize-identity-base", "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-2026-98475", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel s390: channel measurement block uses wrong address type

On s390 Linux kernels built with CONFIG_RANDOMIZE_IDENTITY_BASE, the channel measurement facility passes a virtual address where firmware expects an absolute address. Firmware then stores extended channel measurement data at the wrong location, which is a correctness bug rather than a clear attack path.

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

## How to check

- Check whether the kernel is built with `CONFIG_RANDOMIZE_IDENTITY_BASE=y` in the kernel config, for example `grep RANDOMIZE_IDENTITY_BASE /boot/config-$(uname -r)`
- Check whether the host is an IBM Z (s390x) system using channel measurement data, which the sources do not detail further

## Fix

- Update the Linux kernel to a release that includes the upstream commit titled 's390/cmf: Fix virtual vs physical address confusion' (exact fixed version: unknown)

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98475

## From the sources

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

s390/cmf: Fix virtual vs physical address confusion

The measurement block address is an absolute address. Define the
associated schib_config and schib fields as dma64_t to enable automatic
detection of incorrect assignments. Also add the missing virt_to_dma64()
translation.

Without this fix, a wrong address will be used by firmware when storing
extended format channel measurement data on kernels built with
CONFIG_RANDOMIZE_IDENTITY_BASE=y.

---

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