# CVE-2026-98650: KVM: s390: Fix potential races in dat skey functions

> A race condition in Linux KVM s390 storage key functions can cause system crashes, requiring local privileged access to exploit.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-98650, GHSA-mmwf-2qgq-f8xq, UBUNTU-CVE-2026-98650

## What is CVE-2026-98650?

CVE-2026-98650 is a vulnerability in Linux, published on 18 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:

KVM: s390: Fix potential races in dat skey functions

When dat_cond_set_storage_key() finds a large page, it will
conditionally set the storage key in absolute memory using
large_crste_to_phys() to get the absolute address.

There is a race window between dat_entry_walk() and
large_crste_to_phys(): the large page could have been split
concurrently, and large_crste_to_phys() might be called with a crste
that does not designate a large page, leading to crashes.

Similar issues were also present in dat_set_storage_key().

dat_get_storage_key() and dat_reset_reference_bit() did instead check
for a potential concurrent splitting of the large page, but then
handled it incorrectly.

Fix by performing a READ_ONCE on the crste pointer, checking and using
the result, instead of dereferencing the pointer again. In case a race
is detacted, try dat_entry_walk() again.

## Which versions are affected by CVE-2026-98650?


## How do I fix CVE-2026-98650?

Apply the vendor's patch.

## Is CVE-2026-98650 being exploited?

There is no known exploitation of CVE-2026-98650 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98650 and fix it if it is affected.

What it is: CVE-2026-98650 is a vulnerability in Linux, published on 18 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-2026-98650 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-2026-98650/ (Markdown: https://insights.sbomify.com/CVE-2026-98650/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98650
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98650
- OSV: https://osv.dev/vulnerability/CVE-2026-98650

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98650/
Summaries are generated and may contain mistakes; the official description above is the record.