CVE-2026-72172 mm/mm_init: fix uninitialized struct pages for ZONE_DEVICE
An attacker with DAX hotplug capabilities can cause kernel crashes by triggering uninitialized struct pages in early memory sections.
- 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-2026-72172?
CVE-2026-72172 is a high-severity vulnerability in Linux, published on 15 Aug 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/mm_init: fix uninitialized struct pages for ZONE_DEVICE
If DAX memory is hotplugged into an unoccupied subsection of an early section, section_activate() reuses the unoptimized boot memmap. However, compound_nr_pages() still assumes that vmemmap optimization is in effect and initializes only the reduced number of struct pages. As a result, the remaining tail struct pages are left uninitialized, which can later lead to unexpected behavior or crashes.
Fix this by treating early sections as unoptimized when calculating how many struct pages to initialize.
Which versions are affected by CVE-2026-72172?
How do I fix CVE-2026-72172?
Apply the vendor's patch.
Is CVE-2026-72172 being exploited?
There is no known exploitation of CVE-2026-72172 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72172, DEBIAN-CVE-2026-72172, GHSA-535q-qpmg-c9q4, UBUNTU-CVE-2026-72172.