---
id: "CVE-2026-99230"
kind: "vulnerability"
aliases: ["CVE-2026-99230"]
title: "Linux kernel: io_uring futex wait can crash the kernel after command reuse"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["infrastructure", "io_uring", "kernel", "linux", "ublk"]
not_affected_if: ["io-uring-disabled"]
published_at: "2026-11-02T16:17:47+00:00"
first_seen_at: "2026-11-02T16:24:06+00:00"
updated_at: "2026-11-02T16:26:54+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99230", "first_seen_at": "2026-11-02T16:24:06+00:00"}]
---

# Linux kernel: io_uring futex wait can crash the kernel after command reuse

A flaw in the Linux kernel's io_uring subsystem leaves a stale list pointer in a recycled request, so a woken vectored futex wait can dereference it. The sources describe a general protection fault (kernel crash) and do not state that an attacker can run code.

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

## How to check

- Run `uname -r` and compare the kernel version with the fixed versions in the kernel stable branches once published.
- Check whether io_uring is enabled: `cat /proc/sys/kernel/io_uring_disabled` (unknown whether this is conclusive).
- Check whether ublk (`ublk_drv`) is loaded with `lsmod | grep ublk`, since the sources cite a ublk FETCH_REQ path.

## Timeline

- 2026-11-02T16:24:06+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99230

## From the sources

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

io_uring/cmd: don't leave list poison in ->hash_node

io_uring_cmd_del_cancelable() uses hlist_del() to take a command off
->cancelable_uring_cmd, which leaves LIST_POISON1/2 behind in
->hash_node. Requests are recycled through the request cache without
being reinitialised, and not every user of ->hash_node sets it up before
it is used:

If a vectored futex wait is woken while futex_wait_multiple_setup() is
still queueing the futexes, io_futexv_wait() doesn't add the request to
->futex_list, and leaves the completion to the task_work queued by the
wake up. io_futexv_complete() ends in __io_futex_complete(), whose
hlist_del_init() is fine for a request that is unhashed, which is how all
other users of the node leave it. If the request was a cancelable
uring_cmd in its previous life, e.g. a ublk FETCH_REQ, it writes through
LIST_POISON2:

  Oops: general protection fault, probably for non-canonical address
  KASAN: maybe wild-memory-access in range [0xdead000000000120-...]
  RIP: 0010:io_futexv_complete+0x219/0x420
  Call Trace:
   tctx_task_work_run+0x804/0x950
   tctx_task_work+0x71/0xa0
   task_work_run+0x118/0x200

Leave the node unhashed.

---

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