# CVE-2026-23234: f2fs: fix to avoid UAF in f2fs_write_end_io()

> A use-after-free vulnerability in the Linux kernel's f2fs filesystem allows local attackers to potentially execute code or escalate privileges via a race condition during unmount.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 4 Mar 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-23234, DEBIAN-CVE-2026-23234, GHSA-chrj-6658-798c, ROOT-OS-DEBIAN-11-CVE-2026-23234, ROOT-OS-DEBIAN-12-CVE-2026-23234, ROOT-OS-DEBIAN-13-CVE-2026-23234, ROOT-OS-UBUNTU-2204-CVE-2026-23234, ROOT-OS-UBUNTU-2404-CVE-2026-23234, UBUNTU-CVE-2026-23234

## What is CVE-2026-23234?

CVE-2026-23234 is a high-severity use after free vulnerability in Linux kernel, published on 4 Mar 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:

f2fs: fix to avoid UAF in f2fs_write_end_io()

As syzbot reported an use-after-free issue in f2fs_write_end_io().

It is caused by below race condition:

loop device				umount
- worker_thread
 - loop_process_work
  - do_req_filebacked
   - lo_rw_aio
    - lo_rw_aio_complete
     - blk_mq_end_request
      - blk_update_request
       - f2fs_write_end_io
        - dec_page_count
        - folio_end_writeback
					- kill_f2fs_super
					 - kill_block_super
					  - f2fs_put_super
					 : free(sbi)
       : get_pages(, F2FS_WB_CP_DATA)
         accessed sbi which is freed

In kill_f2fs_super(), we will drop all page caches of f2fs inodes before
call free(sbi), it guarantee that all folios should end its writeback, so
it should be safe to access sbi before last folio_end_writeback().

Let's relocate ckpt thread wakeup flow before folio_end_writeback() to
resolve this issue.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-23234?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23234?

Apply the vendor's patch.

## Is CVE-2026-23234 being exploited?

There is no known exploitation of CVE-2026-23234 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23234 and fix it if it is affected.

What it is: CVE-2026-23234 is a high-severity use after free vulnerability in Linux kernel, published on 4 Mar 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-2026-23234 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-23234/ (Markdown: https://insights.sbomify.com/CVE-2026-23234/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23234
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23234
- OSV: https://osv.dev/vulnerability/CVE-2026-23234

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23234/
Summaries are generated and may contain mistakes; the official description above is the record.