# CVE-2026-97525: x86/mm/pat: Allocate split page tables as kernel page tables

> Linux kernel flaw allows stale IOTLB entries due to improper page table allocation, potentially causing memory consistency issues.

- **Severity:** High 8.2 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-97525, GHSA-89c6-7qg8-m7m4, UBUNTU-CVE-2026-97525

## What is CVE-2026-97525?

CVE-2026-97525 is a high-severity vulnerability in Linux, published on 25 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:

x86/mm/pat: Allocate split page tables as kernel page tables

A PTE is allocated directly without going through the standard page table
allocation routines (such as pte_alloc_one_kernel()) when the CPA code
splits a large page (__split_large_page()).

This means the page table constructor is never called nor is the page table
marked as a kernel page table.

The former results in the folio associated with the page table not being
marked as a page table (__pagetable_ctor() is never called thus neither is
__folio_set_pgtable()) nor are statistics updated to reflect
it (lruvec_stat_add_folio() is never called).

The latter issue of failing to mark the page table as a kernel page
table (ptdesc_set_kernel() is never called) is far more problematic.

Since commit:

  5ba2f0a15564 ("mm: introduce deferred freeing for kernel page tables")

kernel page table freeing has been batched and since the
subsequent commit:

  e37d5a2d60a3 ("iommu/sva: invalidate stale IOTLB entries for kernel address space")

IOTLB cache entries for kernel page tables have been invalidated upon
being freed.

Since split page tables are freed without this invalidation, the IOTLB
can contain stale entries for them.

Resolve the issue by using the ordinary PTE allocation API at split time.

This results in these kernel page tables invoking a page table constructor,
and thus requires a page table destructor.

Destructors are not always present, like for early allocated direct map
page tables). Conditionally call pagetable_dtor_free() if the PG_table
folio flag for the ptdesc is set, otherwise we free the page table via
pagetable_free().

Regardless of which path is taken page tables marked as kernel page tables,
which now includes split page tables, take the correct route through
pagetable_free_kernel().

There is a user-visible side effect in that split page tables will appear
in nr_page_table_pages in /proc/vmstat (as do other kernel page tables
allocated after early boot), however this is a positive change.

This issue started being markedly problematic after commit:

  5ba2f0a15564 ("mm: introduce deferred freeing for kernel page tables")

so choose this as the Fixes target.

[ dhansen: rephrase in imperative mood ]

## Which versions are affected by CVE-2026-97525?


## How do I fix CVE-2026-97525?

Apply the vendor's patch.

## Is CVE-2026-97525 being exploited?

There is no known exploitation of CVE-2026-97525 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97525 and fix it if it is affected.

What it is: CVE-2026-97525 is a high-severity vulnerability in Linux, published on 25 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-2026-97525 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-2026-97525/ (Markdown: https://insights.sbomify.com/CVE-2026-97525/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97525
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97525
- OSV: https://osv.dev/vulnerability/CVE-2026-97525

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97525/
Summaries are generated and may contain mistakes; the official description above is the record.