# CVE-2026-98400: s390/ipl: Fix NULL deref in kdump without re-IPL parm block

> A NULL pointer dereference in the Linux kernel s390 IPL code causes a crash during kdump when specific boot parameters are missing.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-108167, BELL-CVE-2026-98400, DEBIAN-CVE-2026-98400, GHSA-v8v9-cp6p-qm5r, UBUNTU-CVE-2026-98400

## What is CVE-2026-98400?

CVE-2026-98400 is a vulnerability in Linux, published on 14 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

s390/ipl: Fix NULL deref in kdump without re-IPL parm block

Some IPL types, like HMC FTP boot or QEMU direct kernel boot, might
not provide an IPL parameter block. In this case, reipl_type_init()
selects IPL_TYPE_UNKNOWN, and reipl_block_actual remains NULL.

kdump passes the re-IPL parameter block to the dump kernel through
os_info. Before commit 3b9678472bab ("s390/ipl: correct kdump reipl
block checksum calculation"), the os_info entry was added only for
IPL types which initialized reipl_block_actual. That commit moved the
os_info update to machine_crash_shutdown(), making it unconditional. As
a result, set_os_info_reipl_block() dereferences reipl_block_actual for
IPL_TYPE_UNKNOWN. This may happen to work by chance when address zero
contains readable lowcore data and the resulting empty os_info entry is
ignored by the dump kernel.

Skip the os_info update when no re-IPL parameter block is available.
Kdump then collect the dump and reboot without setting re-IPL parameter
block.

## Which versions are affected by CVE-2026-98400?


## How do I fix CVE-2026-98400?

Apply the vendor's patch.

## Is CVE-2026-98400 being exploited?

There is no known exploitation of CVE-2026-98400 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98400 and fix it if it is affected.

What it is: CVE-2026-98400 is a vulnerability in Linux, published on 14 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98400 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98400/ (Markdown: https://insights.sbomify.com/CVE-2026-98400/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98400
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98400
- OSV: https://osv.dev/vulnerability/CVE-2026-98400

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98400/
Summaries are generated and may contain mistakes; the official description above is the record.