# CVE-2026-93216: mm/page_owner: use memcg_data snapshot to avoid TOCTOU in print_page_owner_memcg()

> A race condition in the Linux kernel page owner tracking can cause a kernel crash if debug VM assertions are enabled.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-103538, BELL-CVE-2026-93216, DEBIAN-CVE-2026-93216, GHSA-rrh5-8w69-2q6j, UBUNTU-CVE-2026-93216

## What is CVE-2026-93216?

CVE-2026-93216 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/page_owner: use memcg_data snapshot to avoid TOCTOU in print_page_owner_memcg()

print_page_owner_memcg() reads page->memcg_data via READ_ONCE() at the
start to guard against tail pages and NULL data.  However, it later
re-reads page->memcg_data locklessly in two places:

1: page_memcg_check(page)

2: PageMemcgKmem(page) (via folio_memcg_kmem(), which includes
   VM_BUG_ON assertions for tail pages and MEMCG_DATA_OBJEXTS)

If the page is concurrently freed and reallocated as a THP tail page or
slab page between these calls, the VM_BUG_ON assertions can trigger on
CONFIG_DEBUG_VM=y builds, crashing the kernel.

Fix both TOCTOU issues by using the memcg_data snapshot throughout.

## Which versions are affected by CVE-2026-93216?


## How do I fix CVE-2026-93216?

Apply the vendor's patch.

## Is CVE-2026-93216 being exploited?

There is no known exploitation of CVE-2026-93216 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93216 and fix it if it is affected.

What it is: CVE-2026-93216 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.
Exploitation: There is no known exploitation of CVE-2026-93216 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-2026-93216/ (Markdown: https://insights.sbomify.com/CVE-2026-93216/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93216
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93216
- OSV: https://osv.dev/vulnerability/CVE-2026-93216

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93216/
Summaries are generated and may contain mistakes; the official description above is the record.