# CVE-2025-40272: mm/secretmem: fix use-after-free race in fault handler

> A race condition in the Linux kernel secret memory fault handler can cause a use-after-free, leading to a system crash.

- **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:** 6 Dec 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-40272, DEBIAN-CVE-2025-40272, GHSA-cv75-hxcc-wfxg, ROOT-OS-DEBIAN-12-CVE-2025-40272, ROOT-OS-DEBIAN-13-CVE-2025-40272, ROOT-OS-UBUNTU-2204-CVE-2025-40272, ROOT-OS-UBUNTU-2404-CVE-2025-40272, UBUNTU-CVE-2025-40272

## What is CVE-2025-40272?

CVE-2025-40272 is a high-severity use after free vulnerability in Linux, published on 6 Dec 2025. 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:

mm/secretmem: fix use-after-free race in fault handler

When a page fault occurs in a secret memory file created with
`memfd_secret(2)`, the kernel will allocate a new folio for it, mark the
underlying page as not-present in the direct map, and add it to the file
mapping.

If two tasks cause a fault in the same page concurrently, both could end
up allocating a folio and removing the page from the direct map, but only
one would succeed in adding the folio to the file mapping.  The task that
failed undoes the effects of its attempt by (a) freeing the folio again
and (b) putting the page back into the direct map.  However, by doing
these two operations in this order, the page becomes available to the
allocator again before it is placed back in the direct mapping.

If another task attempts to allocate the page between (a) and (b), and the
kernel tries to access it via the direct map, it would result in a
supervisor not-present page fault.

Fix the ordering to restore the direct map before the folio is freed.

## Which versions are affected by CVE-2025-40272?


## How do I fix CVE-2025-40272?

Apply the vendor's patch.

## Is CVE-2025-40272 being exploited?

There is no known exploitation of CVE-2025-40272 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40272 and fix it if it is affected.

What it is: CVE-2025-40272 is a high-severity use after free vulnerability in Linux, published on 6 Dec 2025. 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-2025-40272 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-2025-40272/ (Markdown: https://insights.sbomify.com/CVE-2025-40272/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40272
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40272
- OSV: https://osv.dev/vulnerability/CVE-2025-40272

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40272/
Summaries are generated and may contain mistakes; the official description above is the record.