# CVE-2024-39508: io_uring/io-wq: Use set_bit() and test_bit() at worker->flags

> A data race in the Linux kernel io_uring subsystem can lead to concurrency issues and potential denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Jul 2024
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-68111, BELL-CVE-2024-39508, DEBIAN-CVE-2024-39508, GHSA-578w-3jwj-573c, ROOT-OS-DEBIAN-11-CVE-2024-39508, ROOT-OS-DEBIAN-12-CVE-2024-39508, ROOT-OS-UBUNTU-2204-CVE-2024-39508, UBUNTU-CVE-2024-39508

## What is CVE-2024-39508?

CVE-2024-39508 is a high-severity vulnerability in Linux kernel, published on 12 Jul 2024. 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:

io_uring/io-wq: Use set_bit() and test_bit() at worker->flags

Utilize set_bit() and test_bit() on worker->flags within io_uring/io-wq
to address potential data races.

The structure io_worker->flags may be accessed through various data
paths, leading to concurrency issues. When KCSAN is enabled, it reveals
data races occurring in io_worker_handle_work and
io_wq_activate_free_worker functions.

	 BUG: KCSAN: data-race in io_worker_handle_work / io_wq_activate_free_worker
	 write to 0xffff8885c4246404 of 4 bytes by task 49071 on cpu 28:
	 io_worker_handle_work (io_uring/io-wq.c:434 io_uring/io-wq.c:569)
	 io_wq_worker (io_uring/io-wq.c:?)
<snip>

	 read to 0xffff8885c4246404 of 4 bytes by task 49024 on cpu 5:
	 io_wq_activate_free_worker (io_uring/io-wq.c:? io_uring/io-wq.c:285)
	 io_wq_enqueue (io_uring/io-wq.c:947)
	 io_queue_iowq (io_uring/io_uring.c:524)
	 io_req_task_submit (io_uring/io_uring.c:1511)
	 io_handle_tw_list (io_uring/io_uring.c:1198)
<snip>

Line numbers against commit 18daea77cca6 ("Merge tag 'for-linus' of
git://git.kernel.org/pub/scm/virt/kvm/kvm").

These races involve writes and reads to the same memory location by
different tasks running on different CPUs. To mitigate this, refactor
the code to use atomic operations such as set_bit(), test_bit(), and
clear_bit() instead of basic "and" and "or" operations. This ensures
thread-safe manipulation of worker flags.

Also, move `create_index` to avoid holes in the structure.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2024-39508?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-39508?

Apply the vendor's patch.

## Is CVE-2024-39508 being exploited?

There is no known exploitation of CVE-2024-39508 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-39508 and fix it if it is affected.

What it is: CVE-2024-39508 is a high-severity vulnerability in Linux kernel, published on 12 Jul 2024. 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-2024-39508 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2024-39508/ (Markdown: https://insights.sbomify.com/CVE-2024-39508/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-39508
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-39508
- OSV: https://osv.dev/vulnerability/CVE-2024-39508

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-39508/
Summaries are generated and may contain mistakes; the official description above is the record.