# CVE-2026-89518: sched_ext: Fix this_rq() assumptions in dispatch kfuncs

> A race condition in the Linux kernel's sched_ext subsystem can cause deadlocks during core scheduling, leading to 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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-89518, GHSA-45rw-88gp-h7jx, UBUNTU-CVE-2026-89518

## What is CVE-2026-89518?

CVE-2026-89518 is a 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: Fix this_rq() assumptions in dispatch kfuncs

Under core scheduling, dispatch runs from within the core-wide pick and can
target a sibling rq, so ops.dispatch() may execute on a CPU different from
the dispatched rq's. Several kfunc paths assumed the two always coincide:

- scx_dsq_move() decided whether an rq lock is held by testing this_rq()'s
  rq flags and lock-danced accordingly. A dispatch for a sibling took the
  unlocked-context branch and acquired the source rq lock on top of the
  already held dispatched rq lock which could deadlock.

- scx_bpf_sub_dispatch() dispatched this_rq() with its stashed
  sub_dispatch_prev, which is NULL when dispatching for a sibling.

- finish_dispatch(), scx_bpf_dsq_reenq() and scx_bpf_dsq_nr_queued()
  resolved SCX_DSQ_LOCAL to this CPU's local DSQ rather than the dispatched
  rq's. The latter two are callable from other rq-locked operations too,
  where SCX_DSQ_LOCAL now likewise resolves to the op's rq. This changes
  behavior also without core scheduling, e.g. for ops.enqueue() running a
  remote wakeup on the waking CPU, and is intended: which CPU happens to
  execute an operation is incidental, the op's rq is what it is operating
  on, and the resolution now matches the insert side where SCX_DSQ_LOCAL
  dispatches land on the task's rq.

Use the rq tracked by scx_locked_rq(), which is set to the dispatched rq
around ops invocations and NULL in unlocked contexts.

## Which versions are affected by CVE-2026-89518?


## How do I fix CVE-2026-89518?

Apply the vendor's patch.

## Is CVE-2026-89518 being exploited?

There is no known exploitation of CVE-2026-89518 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89518 and fix it if it is affected.

What it is: CVE-2026-89518 is a 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-2026-89518 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-2026-89518/ (Markdown: https://insights.sbomify.com/CVE-2026-89518/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89518
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89518
- OSV: https://osv.dev/vulnerability/CVE-2026-89518

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89518/
Summaries are generated and may contain mistakes; the official description above is the record.