---
id: CVE-2026-98858
title: 'io_uring: fix task_work add use-after-free with SQPOLL'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  io_uring: fix task_work add use-after-free with SQPOLL

  For SQPOLL, the sqpoll thread runs task_work off its own list and
  doesn't need to be told about it, so it can po…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= af5d68f8892f8ee8f137648b79ceb2abc153a19b <
    42b3332efacfd2140be4cd0dedad4fb96b8ae90e
  - >-
    Linux >= af5d68f8892f8ee8f137648b79ceb2abc153a19b <
    891bd8335a0de3bb15c3b797ce3026bbb0dbef6c
  - >-
    Linux >= af5d68f8892f8ee8f137648b79ceb2abc153a19b <
    395b25968fe854d4efaa19a8e9b7a5b6d1b3eea3
  - >-
    Linux >= af5d68f8892f8ee8f137648b79ceb2abc153a19b <
    a92193c91e8839fe5fc209616ea95465ae4b919d
  - Linux 6.9
published: '2026-10-18'
updated: '2026-10-18'
sourceUpdated: '2026-10-18T15:51:19.578Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-98858'
references:
  - url: 'https://git.kernel.org/stable/c/42b3332efacfd2140be4cd0dedad4fb96b8ae90e'
  - url: 'https://git.kernel.org/stable/c/891bd8335a0de3bb15c3b797ce3026bbb0dbef6c'
  - url: 'https://git.kernel.org/stable/c/395b25968fe854d4efaa19a8e9b7a5b6d1b3eea3'
  - url: 'https://git.kernel.org/stable/c/a92193c91e8839fe5fc209616ea95465ae4b919d'
tags:
  - cve.org
ingestedAt: '2026-10-18T16:47:32.461Z'
---

## Overview

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

io_uring: fix task_work add use-after-free with SQPOLL

For SQPOLL, the sqpoll thread runs task_work off its own list and
doesn't need to be told about it, so it can pop and complete a request
as soon as mpscq_push() has published it. If that was the last request
holding the ring alive, io_ring_exit_work() then frees the ctx, stops
the thread, and with it the tctx, while io_req_normal_work_add() is
still looking at both after the push:

  BUG: KASAN: slab-use-after-free in io_req_normal_work_add+0x439/0x510
  Read of size 4 at addr ff11000000ca0000 by task repro/55
  (...)
  BUG: KASAN: slab-use-after-free in queue_work_on+0x25/0x70
  Write of size 8 at addr ff11000000c3bd00 by task repro/55

Hold an RCU read lock across the add, like io_req_local_work_add() already
does, and have io_ring_exit_work() wait for a grace period for SQPOLL rings
as well before freeing the ctx.

## Affected

- `Linux >= af5d68f8892f8ee8f137648b79ceb2abc153a19b < 42b3332efacfd2140be4cd0dedad4fb96b8ae90e`
- `Linux >= af5d68f8892f8ee8f137648b79ceb2abc153a19b < 891bd8335a0de3bb15c3b797ce3026bbb0dbef6c`
- `Linux >= af5d68f8892f8ee8f137648b79ceb2abc153a19b < 395b25968fe854d4efaa19a8e9b7a5b6d1b3eea3`
- `Linux >= af5d68f8892f8ee8f137648b79ceb2abc153a19b < a92193c91e8839fe5fc209616ea95465ae4b919d`
- `Linux 6.9`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.