# CVE-2026-98219: sched_ext: Close the pre-enable ops error claim window

> A race condition in the Linux kernel's sched_ext subsystem allows a use-after-free, potentially leading to privilege escalation or code execution.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-98219, GHSA-fmhg-ffq7-4rm5, UBUNTU-CVE-2026-98219

## What is CVE-2026-98219?

CVE-2026-98219 is an use after free vulnerability in Linux, published on 6 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: Close the pre-enable ops error claim window

scx_alloc_and_add_sched() publishes ops->priv before
scx_root_enable_workfn() switches the state to SCX_ENABLING. An error
claimed via scx_bpf_error_bstr() from an associated BPF program in that
window is consumed by scx_disable_workfn(), which takes the pre-enable
shortcut in scx_root_disable(). The shortcut returns without any teardown
and restores SCX_DISABLED with an unconditional scx_set_enable_state() xchg
racing the enable workfn's own transition. The enable then completes with
the claim consumed: the scheduler stays up but can never be disabled again,
and bpf_scx_unreg() frees it while still in use, resulting in a
use-after-free. Both WARN_ON_ONCE()s fire back to back:

  WARNING: kernel/sched/ext/ext.c:7522 at
  scx_root_enable_workfn+0xeec/0x1be0, CPU#3: scx_enable_help/276

  WARNING: kernel/sched/ext/ext.c:6398 at scx_root_disable+0xb50/0xdb8,
  CPU#0: sched_ext_helpe/664

scx_root_enable_workfn() switches to SCX_ENABLING before the scheduler
allocation, so ops->priv is never visible while SCX_DISABLED. The allocation
failure path restores SCX_DISABLED.

## Which versions are affected by CVE-2026-98219?


## How do I fix CVE-2026-98219?

Apply the vendor's patch.

## Is CVE-2026-98219 being exploited?

There is no known exploitation of CVE-2026-98219 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98219 and fix it if it is affected.

What it is: CVE-2026-98219 is an use after free vulnerability in Linux, published on 6 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-2026-98219 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-2026-98219/ (Markdown: https://insights.sbomify.com/CVE-2026-98219/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98219
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98219
- OSV: https://osv.dev/vulnerability/CVE-2026-98219

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98219/
Summaries are generated and may contain mistakes; the official description above is the record.