# CVE-2026-43389: mm: memfd_luo: always dirty all folios


- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 8 May 2026
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2026-43389, GHSA-rmwg-23c2-w7hq, UBUNTU-CVE-2026-43389

## What is CVE-2026-43389?

CVE-2026-43389 is a medium-severity vulnerability in Linux kernel, published on 8 May 2026. 

### Official description

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

mm: memfd_luo: always dirty all folios

A dirty folio is one which has been written to.  A clean folio is its
opposite.  Since a clean folio has no user data, it can be freed under
memory pressure.

memfd preservation with LUO saves the flag at preserve().  This is
problematic.  The folio might get dirtied later.  Saving it at freeze()
also doesn't work, since the dirty bit from PTE is normally synced at
unmap and there might still be mappings of the file at freeze().

To see why this is a problem, say a folio is clean at preserve, but gets
dirtied later.  The serialized state of the folio will mark it as clean. 
After retrieve, the next kernel will see the folio as clean and might try
to reclaim it under memory pressure.  This will result in losing user
data.

Mark all folios of the file as dirty, and always set the
MEMFD_LUO_FOLIO_DIRTY flag.  This comes with the side effect of making all
clean folios un-reclaimable.  This is a cost that has to be paid for
participants of live update.  It is not expected to be a common use case
to preserve a lot of clean folios anyway.

Since the value of pfolio->flags is a constant now, drop the flags
variable and set it directly.

## Which versions are affected by CVE-2026-43389?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43389?

Upgrade to a fixed version.

## Is CVE-2026-43389 being exploited?

There is no known exploitation of CVE-2026-43389 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-2026-43389 and fix it if it is affected.

What it is: CVE-2026-43389 is a medium-severity vulnerability in Linux kernel, published on 8 May 2026. 
Exploitation: There is no known exploitation of CVE-2026-43389 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-2026-43389/ (Markdown: https://insights.sbomify.com/CVE-2026-43389/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43389
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43389
- OSV: https://osv.dev/vulnerability/CVE-2026-43389

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43389/
Summaries are generated and may contain mistakes; the official description above is the record.