# CVE-2026-90187: null_blk: free zones array on device power-off

> A memory leak in the Linux kernel null_blk driver allows local attackers to exhaust system memory by repeatedly toggling zoned device power states.

- **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:** 17 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-102177, BELL-CVE-2026-90187, DEBIAN-CVE-2026-90187, GHSA-45hh-qmfr-m7pj, UBUNTU-CVE-2026-90187

## What is CVE-2026-90187?

CVE-2026-90187 is a memory corruption vulnerability in Linux, published on 17 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:

null_blk: free zones array on device power-off

null_init_zoned_dev() allocates dev->zones when a zoned device is powered
on, but null_del_dev() never frees it on power-off; dev->zones is only
freed later in null_free_dev(), when the configfs directory is removed. If
the device is powered off and then on again, null_init_zoned_dev()
allocates a new array and overwrites the dev->zones pointer, leaking the
previous allocation each power cycle.

Free dev->zones in null_del_dev() via null_free_zoned_dev() to solve it.
And calling null_free_zoned_dev() in null_free_dev() is no longer necessary
because every caller already invokes null_del_dev() first: via
nullb_group_drop_item() before nullb_device_release(), in the
null_add_dev() error path of null_create_dev(), and in null_destroy_dev().
Remove the redundant call.

And take &lock around zone_cond_store() in the two store wrappers to
serialize dev->zones check-and-deref against its alloc/free, which already
run under &lock. The reason there was no problem before is that only
nullb_device_release() or null_exit() frees the dev->zones, which
guarantees that subsequent users won't access the configfs interface.

## Which versions are affected by CVE-2026-90187?


## How do I fix CVE-2026-90187?

Apply the vendor's patch.

## Is CVE-2026-90187 being exploited?

There is no known exploitation of CVE-2026-90187 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90187 and fix it if it is affected.

What it is: CVE-2026-90187 is a memory corruption vulnerability in Linux, published on 17 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-2026-90187 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-2026-90187/ (Markdown: https://insights.sbomify.com/CVE-2026-90187/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90187
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90187
- OSV: https://osv.dev/vulnerability/CVE-2026-90187

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90187/
Summaries are generated and may contain mistakes; the official description above is the record.