# CVE-2026-93218: mm/huge_memory: skip device-private PMDs in madvise_free_huge_pmd

> A race condition in the Linux kernel memory management allows a local attacker to trigger a kernel panic via a device-private PMD during madvise operations.

- **Severity:** Not scored
- **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:** 24 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-93218, GHSA-xw3m-6qvq-wwvg, UBUNTU-CVE-2026-93218

## What is CVE-2026-93218?

CVE-2026-93218 is a vulnerability in Linux, published on 24 Sep 2026. 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/huge_memory: skip device-private PMDs in madvise_free_huge_pmd

madvise_free_pte_range() checks pmd_trans_huge(*pmd) unlocked, then
madvise_free_huge_pmd() takes pmd_trans_huge_lock().  pmd_is_huge()
returns true for a device-private PMD, so orig_pmd can be device-private
and enter the !pmd_present() branch.

Skip device-private PMDs in that non-present branch and continue to out
before calling pmd_folio().  Downgrade the check to VM_WARN_ON_ONCE() so
an unexpected PMD softleaf logs a warning rather than panicking.  Drop the
thp_migration_supported() guard: it expands to
IS_ENABLED(CONFIG_ARCH_SUPPORTS_PMD_SOFTLEAF), and both
pmd_is_migration_entry() and pmd_is_device_private_entry() already return
false when that config is not selected, so the guard suppresses only the
case where the warning would already be silent.

Potential trigger: an HMM-based GPU driver races with madvise(MADV_FREE):
migrate_vma_pages() flips the PMD to a device-private entry between the
caller's pmd_trans_huge() check and the callee's pmd_trans_huge_lock().

## Which versions are affected by CVE-2026-93218?


## How do I fix CVE-2026-93218?

Apply the vendor's patch.

## Is CVE-2026-93218 being exploited?

There is no known exploitation of CVE-2026-93218 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93218 and fix it if it is affected.

What it is: CVE-2026-93218 is a vulnerability in Linux, published on 24 Sep 2026. 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-2026-93218 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-2026-93218/ (Markdown: https://insights.sbomify.com/CVE-2026-93218/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93218
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93218
- OSV: https://osv.dev/vulnerability/CVE-2026-93218

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93218/
Summaries are generated and may contain mistakes; the official description above is the record.