---
id: "CVE-2026-99130"
kind: "vulnerability"
aliases: ["CVE-2026-99130"]
title: "Linux kernel: io_uring exit can spin a CPU and panic with panic_on_warn"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["io_uring", "linux-kernel", "multi-user-hosts", "runtime", "self-hosted"]
not_affected_if: ["io_uring-disabled", "no-untrusted-local-users"]
published_at: "2026-10-28T11:17:32+00:00"
first_seen_at: "2026-10-28T11:32:35+00:00"
updated_at: "2026-10-28T11:36:19+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99130", "first_seen_at": "2026-10-28T11:32:35+00:00"}]
---

# Linux kernel: io_uring exit can spin a CPU and panic with panic_on_warn

A disabled io_uring ring whose submitter is another task can leave an exiting thread spinning in the kernel instead of sleeping. An unprivileged local user can trigger it on purpose, and with panic_on_warn set the kernel panics.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- `uname -r` and compare against the kernel version that carries the io_uring/cancel fix (the sources do not list fixed versions)
- Check whether io_uring is enabled for unprivileged users: `sysctl kernel.io_uring_disabled`
- Check for panic_on_warn: `sysctl kernel.panic_on_warn`

## Fix

- Update the Linux kernel to a release that includes the io_uring/cancel fix (fixed version: unknown in sources)
- Until patched, consider `sysctl -w kernel.io_uring_disabled=2` if io_uring is not needed

## Timeline

- 2026-10-28T11:32:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99130

## From the sources

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

io_uring/cancel: don't spin on local work the task can't run

io_uring_cancel_generic() refuses to sleep while any ring on the exiting
task's tctx has local work pending. It assumes the task is that ring's
submitter and that the next io_uring_try_cancel_requests() pass will run
the work. This does not hold for a ring that was still
IORING_SETUP_R_DISABLED when the task got its tctx node from
io_uring_create() or io_ringfd_register(). The submitter is set later by
IORING_REGISTER_ENABLE_RINGS, possibly from another task, and only the
submitter may run local work on an IORING_SETUP_DEFER_TASKRUN ring. To
the exiting task the work stays pending forever, the loop never reaches
schedule(), and the task trips the WARN_ON_ONCE() once and then spins in
do_exit().

An unprivileged user can set this up at will by creating a disabled
ring, having a child enable it and stop, posting to the ring with
IORING_OP_MSG_RING and exiting with a request in flight that only the
child can complete. The exiting thread burns a CPU until the child runs
or dies, and with panic_on_warn set the WARN panics the kernel.

Fix by skipping the sleep only when io_allowed_defer_tw_run() allows the
task to run the work. This is reasonable since work it cannot run cannot
complete any of its requests either, so nothing is lost by sleeping.
Drop the WARN_ON_ONCE() since handing a disabled ring to another thread
is a supported scenario, not a bug state.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_