# CVE-2025-38085: mm/hugetlb: fix huge_pmd_unshare() vs GUP-fast race

> A race condition in the Linux kernel's hugetlb subsystem allows concurrent GUP-fast operations to access incorrect page tables, potentially causing unexpected behavior.

- **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:** 28 Jun 2025
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-64380, BELL-CVE-2025-38085, DEBIAN-CVE-2025-38085, GHSA-5q6f-wm2q-mpgg, ROOT-OS-DEBIAN-11-CVE-2025-38085, ROOT-OS-DEBIAN-12-CVE-2025-38085, ROOT-OS-UBUNTU-2204-CVE-2025-38085, ROOT-OS-UBUNTU-2404-CVE-2025-38085, UBUNTU-CVE-2025-38085

## What is CVE-2025-38085?

CVE-2025-38085 is a high-severity vulnerability in Debian Debian Linux, published on 28 Jun 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/hugetlb: fix huge_pmd_unshare() vs GUP-fast race

huge_pmd_unshare() drops a reference on a page table that may have
previously been shared across processes, potentially turning it into a
normal page table used in another process in which unrelated VMAs can
afterwards be installed.

If this happens in the middle of a concurrent gup_fast(), gup_fast() could
end up walking the page tables of another process.  While I don't see any
way in which that immediately leads to kernel memory corruption, it is
really weird and unexpected.

Fix it with an explicit broadcast IPI through tlb_remove_table_sync_one(),
just like we do in khugepaged when removing page tables for a THP
collapse.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2025-38085?

It affects 2 products.


Products: Debian Debian Linux, Linux kernel.

## How do I fix CVE-2025-38085?

Apply the vendor's patch.

## Is CVE-2025-38085 being exploited?

There is no known exploitation of CVE-2025-38085 in the wild and no public exploit code.

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-38085 and fix it if it is affected.

What it is: CVE-2025-38085 is a high-severity vulnerability in Debian Debian Linux, published on 28 Jun 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-2025-38085 in the wild and no public exploit code.

Affected product: Debian Debian 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-2025-38085/ (Markdown: https://insights.sbomify.com/CVE-2025-38085/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-38085
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-38085
- OSV: https://osv.dev/vulnerability/CVE-2025-38085

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-38085/
Summaries are generated and may contain mistakes; the official description above is the record.