# CVE-2026-89458: s390/dasd: Do not complete a failed ESE read as successful

> A local attacker can read uninitialized memory from failed ESE track reads in the Linux kernel s390/dasd driver, potentially exposing sensitive data.

- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100755, BELL-CVE-2026-89458, DEBIAN-CVE-2026-89458, GHSA-h4qc-9g56-8mx9, UBUNTU-CVE-2026-89458

## What is CVE-2026-89458?

CVE-2026-89458 is a 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:

s390/dasd: Do not complete a failed ESE read as successful

dasd_int_handler() completes an NRF read of an unallocated ESE track by
calling ese_read() and unconditionally marking the request
DASD_CQR_SUCCESS. dasd_eckd_ese_read() can return an error before it has
zeroed the destination buffer: a failed sense-data parse or a current
track outside the requested range both return early, leaving the
destination pages untouched. The request is still completed successfully,
so the block layer is handed stale / uninitialized memory instead of
zeros.

Check the ese_read() return value and fail the request through the normal
error path instead of forcing DASD_CQR_SUCCESS.

## Which versions are affected by CVE-2026-89458?


## How do I fix CVE-2026-89458?

Apply the vendor's patch.

## Is CVE-2026-89458 being exploited?

There is no known exploitation of CVE-2026-89458 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89458 and fix it if it is affected.

What it is: CVE-2026-89458 is a 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-2026-89458 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-2026-89458/ (Markdown: https://insights.sbomify.com/CVE-2026-89458/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89458
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89458
- OSV: https://osv.dev/vulnerability/CVE-2026-89458

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89458/
Summaries are generated and may contain mistakes; the official description above is the record.