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.
- 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
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.
Sources
Also known as DEBIAN-CVE-2026-93218, GHSA-xw3m-6qvq-wwvg, UBUNTU-CVE-2026-93218.