# CVE-2026-98864: sched_ext: Wait for SCX_OPSS_DISPATCHING before reenqueueing a task

> A race condition in the Linux kernel scheduler allows tasks to be dropped during reenqueueing, potentially causing denial of service.

- **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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-98864, GHSA-fpjr-j5w9-j6gm, UBUNTU-CVE-2026-98864

## What is CVE-2026-98864?

CVE-2026-98864 is a vulnerability in Linux, published on 18 Oct 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: Wait for SCX_OPSS_DISPATCHING before reenqueueing a task

ebf1ccff79c4 ("sched_ext: Fix ops.dequeue() semantics") moved the final
ops_state store in scx_dispatch_enqueue() after the DSQ unlock so that the
custody update and ops.dequeue() precede it. A task can thus be found on a
DSQ while still SCX_OPSS_DISPATCHING.

The dequeue and core-sched pick paths wait for the state to clear in
ops_dequeue() but the reenqueue paths don't. A reenqueue in that window runs
ops.enqueue() and sets SCX_OPSS_QUEUED before the dispatch has completed.
The dispatcher's final store then overwrites it with SCX_OPSS_NONE and
finish_dispatch() drops every later dispatch of the task.

Wait for SCX_OPSS_DISPATCHING to clear before dequeueing a task for
reenqueue, the same way ops_dequeue() does.

## Which versions are affected by CVE-2026-98864?


## How do I fix CVE-2026-98864?

Apply the vendor's patch.

## Is CVE-2026-98864 being exploited?

There is no known exploitation of CVE-2026-98864 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98864 and fix it if it is affected.

What it is: CVE-2026-98864 is a vulnerability in Linux, published on 18 Oct 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-2026-98864 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-2026-98864/ (Markdown: https://insights.sbomify.com/CVE-2026-98864/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98864
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98864
- OSV: https://osv.dev/vulnerability/CVE-2026-98864

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98864/
Summaries are generated and may contain mistakes; the official description above is the record.