# CVE-2026-89516: sched_ext: Don't BUG_ON a destroyed DSQ in process_deferred_reenq_users

> A local attacker can trigger a kernel crash by destroying a dispatch queue while a deferred re-enqueue operation is pending.

- **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:** DEBIAN-CVE-2026-89516, GHSA-99wv-m4hp-r266, UBUNTU-CVE-2026-89516

## What is CVE-2026-89516?

CVE-2026-89516 is a denial of service 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:

sched_ext: Don't BUG_ON a destroyed DSQ in process_deferred_reenq_users

scx_bpf_dsq_reenq() queues a deferred reenq (dru) that runs from
run_deferred(), not ops.dispatch(). If the DSQ is destroyed before the dru
runs, process_deferred_reenq_users() sees dsq->id == SCX_DSQ_INVALID and
hits the BUG_ON. destroy_dsq() doesn't flush pending drus, so just skip.

tj: Read dsq->id once with READ_ONCE(). Reading it separately in the INVALID
    check and the BUG_ON would leave a window where destroy_dsq() can
    invalidate the id between the two reads and still trigger the BUG_ON.

## Which versions are affected by CVE-2026-89516?


## How do I fix CVE-2026-89516?

Apply the vendor's patch.

## Is CVE-2026-89516 being exploited?

There is no known exploitation of CVE-2026-89516 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89516 and fix it if it is affected.

What it is: CVE-2026-89516 is a denial of service 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-2026-89516 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-2026-89516/ (Markdown: https://insights.sbomify.com/CVE-2026-89516/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89516
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89516
- OSV: https://osv.dev/vulnerability/CVE-2026-89516

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89516/
Summaries are generated and may contain mistakes; the official description above is the record.