# CVE-2026-89574: dm array: validate array block headers on read

> A missing validation in the Linux kernel dm array driver allows out-of-bounds reads, potentially causing crashes or code execution.

- **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:** 21 Oct 2026
- **Also known as:** AZL-100133, BELL-CVE-2026-89574, DEBIAN-CVE-2026-89574, GHSA-ccr8-4v7h-gw2w, UBUNTU-CVE-2026-89574

## What is CVE-2026-89574?

CVE-2026-89574 is a high-severity memory corruption 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:

dm array: validate array block headers on read

array_block_check() validates blocknr and csum and nothing else, while
node_check(), next to it, has bounded the structural fields since both
were written. dm_array_cursor_next() takes its loop bound from the
on-disk nr_entries and element_at() is unguarded pointer arithmetic, so
a count larger than the block holds keeps the cursor in one block while
the index grows past it and the read walks off the dm-bufio buffer --
dm_cache_load_mappings() drives it once per cache block at activation.

Check the header against itself: reject a zero value_size, require
max_entries to equal calc_max_entries() for that value_size and block
size, and require nr_entries to fit. Equality rather than an upper bound,
since a count below the real capacity trips BUG_ON() in fill_ablock() and
trim_ablock(). Metadata dm-array writes satisfies all three.

## Which versions are affected by CVE-2026-89574?


## How do I fix CVE-2026-89574?

Apply the vendor's patch.

## Is CVE-2026-89574 being exploited?

There is no known exploitation of CVE-2026-89574 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89574 and fix it if it is affected.

What it is: CVE-2026-89574 is a high-severity memory corruption 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-2026-89574 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-2026-89574/ (Markdown: https://insights.sbomify.com/CVE-2026-89574/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89574
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89574
- OSV: https://osv.dev/vulnerability/CVE-2026-89574

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89574/
Summaries are generated and may contain mistakes; the official description above is the record.