# CVE-2024-36001: netfs: Fix the pre-flush when appending to a file in writethrough mode

> A race condition in the Linux kernel netfs subsystem can cause a kernel warning and potential crash when appending to files in writethrough mode.

- **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:** 20 May 2024
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2024-36001, DEBIAN-CVE-2024-36001, GHSA-j5x4-gghq-7xhm, UBUNTU-CVE-2024-36001

## What is CVE-2024-36001?

CVE-2024-36001 is a high-severity memory corruption vulnerability in Linux kernel, published on 20 May 2024. 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:

netfs: Fix the pre-flush when appending to a file in writethrough mode

In netfs_perform_write(), when the file is marked NETFS_ICTX_WRITETHROUGH
or O_*SYNC or RWF_*SYNC was specified, write-through caching is performed
on a buffered file.  When setting up for write-through, we flush any
conflicting writes in the region and wait for the write to complete,
failing if there's a write error to return.

The issue arises if we're writing at or above the EOF position because we
skip the flush and - more importantly - the wait.  This becomes a problem
if there's a partial folio at the end of the file that is being written out
and we want to make a write to it too.  Both the already-running write and
the write we start both want to clear the writeback mark, but whoever is
second causes a warning looking something like:

    ------------[ cut here ]------------
    R=00000012: folio 11 is not under writeback
    WARNING: CPU: 34 PID: 654 at fs/netfs/write_collect.c:105
    ...
    CPU: 34 PID: 654 Comm: kworker/u386:27 Tainted: G S ...
    ...
    Workqueue: events_unbound netfs_write_collection_worker
    ...
    RIP: 0010:netfs_writeback_lookup_folio

Fix this by making the flush-and-wait unconditional.  It will do nothing if
there are no folios in the pagecache and will return quickly if there are
no folios in the region specified.

Further, move the WBC attachment above the flush call as the flush is going
to attach a WBC and detach it again if it is not present - and since we
need one anyway we might as well share it.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2024-36001?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-36001?

Apply the vendor's patch.

## Is CVE-2024-36001 being exploited?

There is no known exploitation of CVE-2024-36001 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-2024-36001 and fix it if it is affected.

What it is: CVE-2024-36001 is a high-severity memory corruption vulnerability in Linux kernel, published on 20 May 2024. 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-2024-36001 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-2024-36001/ (Markdown: https://insights.sbomify.com/CVE-2024-36001/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-36001
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-36001
- OSV: https://osv.dev/vulnerability/CVE-2024-36001

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-36001/
Summaries are generated and may contain mistakes; the official description above is the record.