# CVE-2026-98399: s390/ipl: Fix NULL deref in dump_reipl without re-IPL parm block

> A NULL pointer dereference in the Linux kernel s390 IPL code can cause a denial of service during stand-alone dumps when no re-IPL parameter block is provided.

- **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-108129, BELL-CVE-2026-98399, DEBIAN-CVE-2026-98399, GHSA-wvr7-cc68-fmx4, UBUNTU-CVE-2026-98399

## What is CVE-2026-98399?

CVE-2026-98399 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 dump_reipl without re-IPL parm block

Unlike kdump, which passes the re-IPL parameter block through os_info,
the stand-alone dump passes it through the IPL parm block address and
checksum in lowcore.

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. Nevertheless,
dump_reipl_run() unconditionally dereferences it when preparing the
lowcore fields. This may happen to work by chance when address zero
contains readable lowcore data. A zero IPL parameter block address is
then stored in lowcore, causing the stand-alone dumper to enter disabled
wait after completing the dump.

Explicitly store a zero IPL parameter block address and checksum when no
re-IPL parameter block is available. This does not change the behavior:
the stand-alone dumper completes the dump and halts, while valid re-IPL
parameter blocks continue to be handled as before.

## Which versions are affected by CVE-2026-98399?


## How do I fix CVE-2026-98399?

Apply the vendor's patch.

## Is CVE-2026-98399 being exploited?

There is no known exploitation of CVE-2026-98399 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98399 and fix it if it is affected.

What it is: CVE-2026-98399 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-2026-98399 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-2026-98399/ (Markdown: https://insights.sbomify.com/CVE-2026-98399/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98399
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98399
- OSV: https://osv.dev/vulnerability/CVE-2026-98399

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98399/
Summaries are generated and may contain mistakes; the official description above is the record.