# CVE-2026-93239: arm64: mm: Fix the lockless page-table walk in show_pte()

> A race condition in the Linux kernel arm64 memory management allows a local attacker to cause a system crash via a lockless page-table walk.

- **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:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-93239, DEBIAN-CVE-2026-93239, GHSA-5wwm-gpr7-9rm3, UBUNTU-CVE-2026-93239

## What is CVE-2026-93239?

CVE-2026-93239 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:

arm64: mm: Fix the lockless page-table walk in show_pte()

show_pte() walks page tables locklessly and can run with interrupts
enabled. A concurrent teardown can free a table page while it is being
walked. It can also clear a parent entry after show_pte() checked it; the
regular pXd_offset() helpers then reread the cleared entry and can derive a
bogus lower-level pointer and fault again.

Use the lockless offset helpers with the saved parent entries, as
gup_fast() does, and pass the saved PMD to pte_offset_map().

For task page tables, arm64 selects MMU_GATHER_RCU_TABLE_FREE. Disable
local interrupts around the walk to hold off RCU-deferred table frees and
block the tlb_remove_table_sync_one() IPI until the walk is finished.

Place the IRQ guard after the header print. This does not make the output a
consistent snapshot, but prevents the task page-table walk from
dereferencing a released table page or deriving a pointer from a different
parent value.

## Which versions are affected by CVE-2026-93239?


## How do I fix CVE-2026-93239?

Apply the vendor's patch.

## Is CVE-2026-93239 being exploited?

There is no known exploitation of CVE-2026-93239 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93239 and fix it if it is affected.

What it is: CVE-2026-93239 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-2026-93239 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-2026-93239/ (Markdown: https://insights.sbomify.com/CVE-2026-93239/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93239
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93239
- OSV: https://osv.dev/vulnerability/CVE-2026-93239

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93239/
Summaries are generated and may contain mistakes; the official description above is the record.