# CVE-2026-99103: workqueue: Fix unbound pool lifetime for pending pwqs


- **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-2026-99103, DEBIAN-CVE-2026-99103, GHSA-qwjv-757x-9f99, UBUNTU-CVE-2026-99103

## What is CVE-2026-99103?

CVE-2026-99103 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

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

workqueue: Fix unbound pool lifetime for pending pwqs

KASAN reports a use-after-free of an unbound worker_pool in
node_activate_pending_pwq():

  BUG: KASAN: slab-use-after-free in _raw_spin_trylock+0x6d/0x120
  Read of size 4 at addr ffff8880089ce000 by task kworker/u22:0/318

  CPU: 1 UID: 0 PID: 318 Comm: kworker/u22:0 Not tainted 7.2.0 #1 PREEMPT(lazy)
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
  Workqueue:  0x0 (flush-8:0)
  Call Trace:
   <TASK>
   dump_stack_lvl+0x53/0x70
   print_report+0xce/0x610
   kasan_report+0xce/0x100
   _raw_spin_trylock+0x6d/0x120
   pwq_dec_nr_in_flight+0x4b4/0xcb0
   process_one_work+0x921/0x11a0
   worker_thread+0x4d0/0xd20
   kthread+0x2de/0x3c0
   ret_from_fork+0x3aa/0x620
   ret_from_fork_asm+0x1a/0x30
   </TASK>

  Allocated by task 311:
   alloc_pwq+0x439/0xca0
   apply_wqattrs_prepare+0x75e/0xd10
   apply_workqueue_attrs_locked+0x44/0xa0
   wq_nice_store+0x350/0x450

  Freed by task 0:
   kfree+0x127/0x3b0
   rcu_core+0x523/0x1780
   handle_softirqs+0x1b3/0x610

  Last potentially related work creation:
   put_unbound_pool+0x3f3/0x7d0
   pwq_release_workfn+0x494/0x8e0
   kthread_worker_fn+0x1ff/0x790

Canceling the last inactive work skips pwq_dec_nr_active(), so an empty
pwq can remain on pending_pwqs when its refcnt reaches zero.
pwq_release_workfn() currently puts the pool before removing that pwq.
If this drops the last pool reference, the pool can be RCU-freed while
the pwq remains reachable, and node_activate_pending_pwq() may trylock
the freed pool->lock.

Remove the pwq from pending_pwqs before putting the pool.

## Which versions are affected by CVE-2026-99103?


## How do I fix CVE-2026-99103?

Upgrade to a fixed version.

## Is CVE-2026-99103 being exploited?

There is no known exploitation of CVE-2026-99103 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99103 and fix it if it is affected.

What it is: CVE-2026-99103 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99103 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-2026-99103/ (Markdown: https://insights.sbomify.com/CVE-2026-99103/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99103
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99103
- OSV: https://osv.dev/vulnerability/CVE-2026-99103

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99103/
Summaries are generated and may contain mistakes; the official description above is the record.