# CVE-2026-99105: sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its CPU's local DSQ


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** BELL-CVE-2026-99105, DEBIAN-CVE-2026-99105, GHSA-2gwr-rx6x-67fg, UBUNTU-CVE-2026-99105

## What is CVE-2026-99105?

CVE-2026-99105 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its CPU's local DSQ

With SCX_OPS_ENQ_LAST, the last runnable task on a CPU is passed to
ops.enqueue() instead of being kept running. Exiting tasks without
SCX_OPS_ENQ_EXITING, migration disabled tasks without
SCX_OPS_ENQ_MIGRATION_DISABLED and tasks on an offline rq skip ops.enqueue()
and go straight to the local DSQ. This happens in put_prev_task_scx() after
the pick has settled on idle, so nothing reschedules the CPU, which idles
with the task queued until an unrelated wakeup lands on it or the watchdog
fires.

scx_mitosis, which sets SCX_OPS_ENQ_LAST without SCX_OPS_ENQ_EXITING, hit
this during mass cgroup teardown: exiting tasks stuck in exit_mmap() for
over 40 seconds.

A task put on the local DSQ runs, as anywhere else. If the SCX_ENQ_LAST
enqueue left the task on this CPU's local DSQ, set need_resched on the task
being switched in, as proxy_resched_idle() does. resched_curr() would flag
the task being put instead, and __schedule() clears that right after the
pick.

## Which versions are affected by CVE-2026-99105?


## How do I fix CVE-2026-99105?

Upgrade to a fixed version.

## Is CVE-2026-99105 being exploited?

There is no known exploitation of CVE-2026-99105 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99105 and fix it if it is affected.

What it is: CVE-2026-99105 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99105 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-2026-99105/ (Markdown: https://insights.sbomify.com/CVE-2026-99105/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99105
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99105
- OSV: https://osv.dev/vulnerability/CVE-2026-99105

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99105/
Summaries are generated and may contain mistakes; the official description above is the record.