# CVE-2026-89760: mm, swap: don't free a hibernation slot that is in the swap cache

> A Linux kernel swap management bug allows silent memory corruption and crashes when hibernation slots are freed while cached, impacting system stability.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-89760, GHSA-jf6f-8m48-j65r, UBUNTU-CVE-2026-89760

## What is CVE-2026-89760?

CVE-2026-89760 is a high-severity memory corruption vulnerability in Linux, published on 11 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, swap: don't free a hibernation slot that is in the swap cache

A slot with a folio in the swap cache is freed when the folio leaves the
cache, not when its count drops.  swap_put_entries_cluster() follows that
rule.  swap_free_hibernation_slot() does not, it calls
__swap_cluster_free_entries() whether or not a folio sits on the slot.

Cluster readahead can put one there.  It walks a raw page_cluster sized
window of offsets around the faulting entry, and a hibernation slot passes
__swap_cache_add_check() because it is not a folio and its count is not
zero.  Freeing the slot then clears the entry under that folio.

The folio is now unreachable from the swap table, and the offset goes back
to the allocator.  The folio is still on the LRU though, so reclaim can
pick it up later.  It then takes the old offset out of folio->swap and
overwrites the table entry there, which by then may belong to someone
else.

This bug can trigger silent memory corruption, process crashes, or data
instability across completely unrelated userspace applications - typically
occurring when uswsusp is preparing the hibernation image.

I found this while working on giving hibernation slots their own marker in
the swap table, which I had discussed with Kairui. 
(https://lore.kernel.org/linux-mm/abp7aDgYLrxF3Me8@KASONG-MC4/) As far as
I know there are no reports, so there is no Reported-by/Closes to add.

Check for a cached folio before freeing.  The slot is then left in the
ordinary state where only the swap cache holds it, and it is freed when
the folio leaves the cache, either through the reclaim below or through
normal reclaim later.

## Which versions are affected by CVE-2026-89760?


## How do I fix CVE-2026-89760?

Apply the vendor's patch.

## Is CVE-2026-89760 being exploited?

There is no known exploitation of CVE-2026-89760 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89760 and fix it if it is affected.

What it is: CVE-2026-89760 is a high-severity memory corruption vulnerability in Linux, published on 11 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-2026-89760 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-2026-89760/ (Markdown: https://insights.sbomify.com/CVE-2026-89760/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89760
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89760
- OSV: https://osv.dev/vulnerability/CVE-2026-89760

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89760/
Summaries are generated and may contain mistakes; the official description above is the record.