# CVE-2026-90276: md/md-llbitmap: stop daemon timer rearm on destroy

> A use-after-free vulnerability in the Linux kernel's md/llbitmap module allows attackers to cause a denial of service or potentially execute code during device teardown.

- **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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-90276, DEBIAN-CVE-2026-90276, GHSA-wg47-q44p-vcm3, UBUNTU-CVE-2026-90276

## What is CVE-2026-90276?

CVE-2026-90276 is an use after free 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:

md/md-llbitmap: stop daemon timer rearm on destroy

llbitmap_destroy() deletes pending_timer before flushing
md_llbitmap_io_wq. However, daemon_work can still be queued or running
after the timer has been deleted, and the daemon path can arm
pending_timer again when it finds dirty chunks that are not ready to
flush yet.

If that happens during teardown, pending_timer can remain armed after
llbitmap is freed and later dereference freed memory.

Add a BITMAP_SHUTDOWN bit to llbitmap->flags, set it before deleting
the timer, and make the timer and daemon paths stop queueing or rearming
work once teardown starts. Cancel daemon_work before flushing the shared
workqueue so no already queued daemon instance can race with the free.
Use timer_shutdown_sync() so a daemon instance that passed the shutdown
check before teardown cannot rearm the timer afterward.

BITMAP_SHUTDOWN is a runtime-only state. Mask it out when reading and
updating the llbitmap superblock so the shutdown state is never loaded
from disk or persisted to disk.

## Which versions are affected by CVE-2026-90276?


## How do I fix CVE-2026-90276?

Apply the vendor's patch.

## Is CVE-2026-90276 being exploited?

There is no known exploitation of CVE-2026-90276 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90276 and fix it if it is affected.

What it is: CVE-2026-90276 is an use after free 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-2026-90276 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-2026-90276/ (Markdown: https://insights.sbomify.com/CVE-2026-90276/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90276
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90276
- OSV: https://osv.dev/vulnerability/CVE-2026-90276

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90276/
Summaries are generated and may contain mistakes; the official description above is the record.