# CVE-2026-23161: mm/shmem, swap: fix race of truncate and swap entry split

> A race condition in Linux kernel shmem swap handling can cause kernel panics or hangs during stress testing, requiring a patch to fix.

- **Severity:** High 7.3 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/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:** 14 Feb 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-23161, DEBIAN-CVE-2026-23161, GHSA-4rgv-cpg8-f3hr, UBUNTU-CVE-2026-23161

## What is CVE-2026-23161?

CVE-2026-23161 is a high-severity vulnerability in Linux kernel, published on 14 Feb 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/shmem, swap: fix race of truncate and swap entry split

The helper for shmem swap freeing is not handling the order of swap
entries correctly.  It uses xa_cmpxchg_irq to erase the swap entry, but it
gets the entry order before that using xa_get_order without lock
protection, and it may get an outdated order value if the entry is split
or changed in other ways after the xa_get_order and before the
xa_cmpxchg_irq.

And besides, the order could grow and be larger than expected, and cause
truncation to erase data beyond the end border.  For example, if the
target entry and following entries are swapped in or freed, then a large
folio was added in place and swapped out, using the same entry, the
xa_cmpxchg_irq will still succeed, it's very unlikely to happen though.

To fix that, open code the Xarray cmpxchg and put the order retrieval and
value checking in the same critical section.  Also, ensure the order won't
exceed the end border, skip it if the entry goes across the border.

Skipping large swap entries crosses the end border is safe here.  Shmem
truncate iterates the range twice, in the first iteration,
find_lock_entries already filtered such entries, and shmem will swapin the
entries that cross the end border and partially truncate the folio (split
the folio or at least zero part of it).  So in the second loop here, if we
see a swap entry that crosses the end order, it must at least have its
content erased already.

I observed random swapoff hangs and kernel panics when stress testing
ZSWAP with shmem.  After applying this patch, all problems are gone.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-23161?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23161?

Apply the vendor's patch.

## Is CVE-2026-23161 being exploited?

There is no known exploitation of CVE-2026-23161 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23161 and fix it if it is affected.

What it is: CVE-2026-23161 is a high-severity vulnerability in Linux kernel, published on 14 Feb 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-2026-23161 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-23161/ (Markdown: https://insights.sbomify.com/CVE-2026-23161/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23161
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23161
- OSV: https://osv.dev/vulnerability/CVE-2026-23161

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23161/
Summaries are generated and may contain mistakes; the official description above is the record.