---
id: "CVE-2026-99124"
kind: "vulnerability"
aliases: ["CVE-2026-99124"]
title: "Linux s390 PCI: short error report write leaks uninitialized kernel memory"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["ibm-z", "infrastructure", "kernel", "linux", "s390"]
not_affected_if: ["non-s390-architecture"]
published_at: "2026-10-28T11:17:32+00:00"
first_seen_at: "2026-10-28T11:32:35+00:00"
updated_at: "2026-10-28T11:37:29+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99124", "first_seen_at": "2026-10-28T11:32:35+00:00"}]
---

# Linux s390 PCI: short error report write leaks uninitialized kernel memory

The s390 PCI SCLP error reporting interface does not check that a user-supplied buffer is as long as the report length it declares, so a short write lets an out-of-bounds read pull nearby kernel memory into the report. The leaked data only reaches the privileged SCLP service entity, which can already read that memory, so the flaw is an out-of-bounds read and a malformed-report issue rather than a broad data exposure.

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

## How to check

- unknown

## Fix

- unknown

## Timeline

- 2026-10-28T11:32:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99124

## From the sources

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

s390/pci: Fix leak of uninitialized kernel data in SCLP report

While report_error_write() checks that the provided buffer is at least
as large as the header struct, but not that it is large enough to
contain the report with the length claimed by report->length. If
user-space provides a short buffer, meaning a larger report->length than
the actually written payload, up to around 4K of kernel data from past
the kmalloc(len + 1) sized buffer allocated in kernfs_fop_write_iter()
will leak into the SCLP report.

However, as the entity processing the SCLP is privileged and able to
access at least the page including the report, this does not leak data
that entity could not access but it is still an out of bounds read and
a malformed error report that should be rejected.

---

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