# CVE-2026-89919: KVM: s390: keyop: use mmu_lock to read gmap->asce

> A race condition in KVM s390 keyop allows concurrent access to stale memory mappings, potentially leading to memory corruption and privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-89919, GHSA-xrcv-f2mv-23j2, UBUNTU-CVE-2026-89919

## What is CVE-2026-89919?

CVE-2026-89919 is a high-severity vulnerability in Linux, published on 16 Sep 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: keyop: use mmu_lock to read gmap->asce

Every other dat_* consumer in this file (kvm_s390_get_skeys,
set_skeys, get_cmma_bits, set_cmma_bits, MEM_CLR_CMMA,
kvm_s390_fixup_prefix, kvm_test_age_gfn, kvm_age_gfn) reads
kvm->arch.gmap->asce *inside* the mmu_lock read-side. keyop is the only
outlier.

gmap->asce is mutated under write_lock(mmu_lock) by gmap_set_limit()
and keyop might use a stale asce value for walking as KVM_S390_KEYOP
and KVM_S390_VM_MEM_LIMIT_SIZE can run concurrently. This can result
in memory corruption.

## Which versions are affected by CVE-2026-89919?


## How do I fix CVE-2026-89919?

Apply the vendor's patch.

## Is CVE-2026-89919 being exploited?

There is no known exploitation of CVE-2026-89919 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89919 and fix it if it is affected.

What it is: CVE-2026-89919 is a high-severity vulnerability in Linux, published on 16 Sep 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-2026-89919 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-2026-89919/ (Markdown: https://insights.sbomify.com/CVE-2026-89919/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89919
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89919
- OSV: https://osv.dev/vulnerability/CVE-2026-89919

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89919/
Summaries are generated and may contain mistakes; the official description above is the record.