# CVE-2026-98463: sched_ext: Derive SCX_RQ_IN_WAKEUP from the core enqueue flags

> A use-after-free in the Linux kernel scheduler allows local attackers to execute arbitrary code or escalate privileges when sched_ext is enabled.

- **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:** BELL-CVE-2026-98463, DEBIAN-CVE-2026-98463, GHSA-7f2q-69qm-pp4c, UBUNTU-CVE-2026-98463

## What is CVE-2026-98463?

CVE-2026-98463 is an use after free 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: Derive SCX_RQ_IN_WAKEUP from the core enqueue flags

schedule_deferred_locked() skips scheduling a deferred action while
SCX_RQ_IN_WAKEUP is set and relies on the task_woken_scx() call that follows
a wakeup enqueue to run it. enqueue_task_scx() sets the flag from the merged
enqueue flags, which include the flags stashed for a remote activation.
move_remote_task_to_local_dsq() thus sets SCX_RQ_IN_WAKEUP on the
destination rq when the moved task was woken up, although no
task_woken_scx() follows that activation.

An IMMED insert into a busy destination requests a local reenqueue during
that enqueue. The request gets linked but not scheduled and stays pending
until an unrelated wakeup or preemption on that CPU runs the deferred
actions. The IMMED task sits behind the running task in the meantime. If
nothing runs them before the scheduler is disabled, the request outlives the
scheduler and points into its freed per-cpu area, which the next scheduler
dereferences from run_deferred().

Test the core enqueue flags for the wakeup bit. Only the core's wakeup path
is followed by task_woken_scx().

## Which versions are affected by CVE-2026-98463?


## How do I fix CVE-2026-98463?

Apply the vendor's patch.

## Is CVE-2026-98463 being exploited?

There is no known exploitation of CVE-2026-98463 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98463 and fix it if it is affected.

What it is: CVE-2026-98463 is an use after free 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-2026-98463 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-2026-98463/ (Markdown: https://insights.sbomify.com/CVE-2026-98463/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98463
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98463
- OSV: https://osv.dev/vulnerability/CVE-2026-98463

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98463/
Summaries are generated and may contain mistakes; the official description above is the record.