# CVE-2026-80685: mm/util: don't read __page_2 for order-1 folios in snapshot_page()

> A kernel bug causes a crash when reading non-existent memory during page snapshot operations, leading to denial of service.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H`)
- **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:** 28 Aug 2026
- **Updated:** 21 Sep 2026
- **Also known as:** BELL-CVE-2026-80685, DEBIAN-CVE-2026-80685, GHSA-ccm4-344c-hjv9, UBUNTU-CVE-2026-80685

## What is CVE-2026-80685?

CVE-2026-80685 is a high-severity vulnerability in Linux, published on 28 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/util: don't read __page_2 for order-1 folios in snapshot_page()

snapshot_page() currently reads __page_2 after checking nr_pages > 1, but
it should only do so when nr_pages > 2.

If an order-1 folio is allocated at the end of a vmemmap section,
__page_2 will not exist and reading it will cause a fault.

During DLPAR memory remove on a 22 TB ppc64le LPAR, snapshot_page() oopsed
on the page isolation path while reading an order-1 folio's __page_2 from
an adjacent absent section (unmapped vmemmap).

Fix this to avoid reading memmap that doesn't exist (e.g., a vmemmap
hole).

## Which versions are affected by CVE-2026-80685?


## How do I fix CVE-2026-80685?

Apply the vendor's patch.

## Is CVE-2026-80685 being exploited?

There is no known exploitation of CVE-2026-80685 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80685 and fix it if it is affected.

What it is: CVE-2026-80685 is a high-severity vulnerability in Linux, published on 28 Aug 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-2026-80685 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-2026-80685/ (Markdown: https://insights.sbomify.com/CVE-2026-80685/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80685
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80685
- OSV: https://osv.dev/vulnerability/CVE-2026-80685

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80685/
Summaries are generated and may contain mistakes; the official description above is the record.