# CVE-2026-98858: io_uring: fix task_work add use-after-free with SQPOLL

> A use-after-free in the Linux kernel's io_uring SQPOLL mode allows local attackers to execute arbitrary code or escalate privileges.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98858, DEBIAN-CVE-2026-98858, GHSA-v42g-qm29-227m, UBUNTU-CVE-2026-98858

## What is CVE-2026-98858?

CVE-2026-98858 is an use after free vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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.

## Which versions are affected by CVE-2026-98858?


## How do I fix CVE-2026-98858?

Apply the vendor's patch.

## Is CVE-2026-98858 being exploited?

There is no known exploitation of CVE-2026-98858 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98858 and fix it if it is affected.

What it is: CVE-2026-98858 is an use after free vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98858 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98858/ (Markdown: https://insights.sbomify.com/CVE-2026-98858/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98858
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98858
- OSV: https://osv.dev/vulnerability/CVE-2026-98858

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98858/
Summaries are generated and may contain mistakes; the official description above is the record.