CVE-2026-89755 mm/migrate_device: clear stale mapping after freeing swapcache

What is CVE-2026-89755?

CVE-2026-89755 is a high-severity use after free vulnerability in Linux, published on 11 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/migrate_device: clear stale mapping after freeing swapcache

__migrate_device_pages() reads the folio mapping before calling folio_free_swap(). When folio_free_swap() succeeds, the folio is removed from the swap cache, but the saved mapping still points to swap_space.

Passing the stale mapping to folio_migrate_mapping() makes it use the mapped-folio path for a folio that is no longer in swapcache. It can then operate on swap_space.i_pages with invalid reference accounting, eventually triggering a folio reference count BUG.

After a successful split, nr still contains the number of pages in the original large folio, although each resulting page is now a separate order-0 folio. Reset nr to 1 so each split folio is processed separately, including its own swapcache removal and mapping lookup.

Refresh the saved mapping after folio_free_swap() so the current folio state is used during migration.

Which versions are affected by CVE-2026-89755?

How do I fix CVE-2026-89755?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-89755 being exploited?

There is no known exploitation of CVE-2026-89755 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-100413, BELL-CVE-2026-89755, DEBIAN-CVE-2026-89755, GHSA-f448-r8g9-p8j7, UBUNTU-CVE-2026-89755.