# CVE-2026-89570: cxl/mce: Make the MCE notifier per-region

> A use-after-free vulnerability in the Linux kernel CXL MCE notifier can cause NULL dereferences and system crashes.

- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89570, DEBIAN-CVE-2026-89570, GHSA-5c9g-7vf9-4pwc, UBUNTU-CVE-2026-89570

## What is CVE-2026-89570?

CVE-2026-89570 is a high-severity use after free vulnerability in Linux, published on 11 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:

cxl/mce: Make the MCE notifier per-region

Flavien Solt reported lifetime issues with the CXL MCE notifier, which
can lead to NULL dereferences and use-after-free in the MCE handler.
The notifier was registered per memory device and stored in 'struct
cxl_memdev_state', even though it only needs the region state (the
region's SPA range and its extended linear cache size).

Instead of keeping the memory device and endpoint alive, the correct fix
is to move the notifier into 'struct cxl_region' and register it from
cxl_region_probe() as it should be a per-region notifier. Setup the
registration to only happen for regions that have an extended linear
cache as that is the only current usage.

Remove cxl_port_get_spa_cache_alias() as it is now dead code.

[ dj: Update dev_warn() when notifier fails due to kconfig. (Ben) ]

## Which versions are affected by CVE-2026-89570?


## How do I fix CVE-2026-89570?

Apply the vendor's patch.

## Is CVE-2026-89570 being exploited?

There is no known exploitation of CVE-2026-89570 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89570 and fix it if it is affected.

What it is: CVE-2026-89570 is a high-severity use after free vulnerability in Linux, published on 11 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-2026-89570 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-2026-89570/ (Markdown: https://insights.sbomify.com/CVE-2026-89570/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89570
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89570
- OSV: https://osv.dev/vulnerability/CVE-2026-89570

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89570/
Summaries are generated and may contain mistakes; the official description above is the record.