# CVE-2026-80955: dm-pcache: fix use-after-free and invalid seg operations in kset_replay()

> A use-after-free vulnerability in the Linux kernel's dm-pcache module allows attackers to potentially execute code or cause a system crash.

- **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:** BELL-CVE-2026-80955, DEBIAN-CVE-2026-80955, GHSA-vjx8-9mvv-9939, UBUNTU-CVE-2026-80955

## What is CVE-2026-80955?

CVE-2026-80955 is a high-severity use after free 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:

dm-pcache: fix use-after-free and invalid seg operations in kset_replay()

In kset_replay, when key->seg_gen is stale (key->seg_gen <
key->cache_pos.cache_seg->gen), cache_key_put(key) is called but then
key->cache_pos.cache_seg is accessed as the argument to cache_seg_get().
This is a use-after-free on the freed key memory. Although mempool
recycled memory is not immediately reclaimed or overwritten in practice,
this is still a potential UAF bug.

Additionally, for expired invalid keys, setting the cache->seg_map bit
and calling cache_seg_get() is unreasonable since the corresponding
segment data is no longer valid.

Fix both issues by moving cache_seg_get() and __set_bit() after the
gen check, so they only execute for valid keys, and using continue to
skip invalid keys.

## Which versions are affected by CVE-2026-80955?


## How do I fix CVE-2026-80955?

Apply the vendor's patch.

## Is CVE-2026-80955 being exploited?

There is no known exploitation of CVE-2026-80955 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80955 and fix it if it is affected.

What it is: CVE-2026-80955 is a high-severity use after free 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-2026-80955 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-2026-80955/ (Markdown: https://insights.sbomify.com/CVE-2026-80955/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80955
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80955
- OSV: https://osv.dev/vulnerability/CVE-2026-80955

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80955/
Summaries are generated and may contain mistakes; the official description above is the record.