# CVE-2025-38447: mm/rmap: fix potential out-of-bounds page table access during batched unmap

> A local attacker can trigger an out-of-bounds page table access in the Linux kernel memory management subsystem, potentially causing a crash or privilege escalation.

- **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:** 25 Jul 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-38447, GHSA-crvf-pv9v-3xvj, UBUNTU-CVE-2025-38447

## What is CVE-2025-38447?

CVE-2025-38447 is a high-severity memory corruption vulnerability in Linux kernel, published on 25 Jul 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/rmap: fix potential out-of-bounds page table access during batched unmap

As pointed out by David[1], the batched unmap logic in
try_to_unmap_one() may read past the end of a PTE table when a large
folio's PTE mappings are not fully contained within a single page
table.

While this scenario might be rare, an issue triggerable from userspace
must be fixed regardless of its likelihood.  This patch fixes the
out-of-bounds access by refactoring the logic into a new helper,
folio_unmap_pte_batch().

The new helper correctly calculates the safe batch size by capping the
scan at both the VMA and PMD boundaries.  To simplify the code, it also
supports partial batching (i.e., any number of pages from 1 up to the
calculated safe maximum), as there is no strong reason to special-case
for fully mapped folios.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2025-38447?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-38447?

Apply the vendor's patch.

## Is CVE-2025-38447 being exploited?

There is no known exploitation of CVE-2025-38447 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-2025-38447 and fix it if it is affected.

What it is: CVE-2025-38447 is a high-severity memory corruption vulnerability in Linux kernel, published on 25 Jul 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-2025-38447 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-2025-38447/ (Markdown: https://insights.sbomify.com/CVE-2025-38447/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38447
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38447
- OSV: https://osv.dev/vulnerability/CVE-2025-38447

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38447/
Summaries are generated and may contain mistakes; the official description above is the record.