# CVE-2026-80956: dm-pcache: only hand out initialized cache segments

> A crafted disk image can cause a null pointer dereference in the Linux kernel dm-pcache module, leading to a system crash.

- **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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-80956, DEBIAN-CVE-2026-80956, GHSA-2r45-hwhh-3hc3, UBUNTU-CVE-2026-80956

## What is CVE-2026-80956?

CVE-2026-80956 is a 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: only hand out initialized cache segments

get_cache_segment() scans the segment map up to cache->n_segs, the
physical device segment count, but cache_segs_init() only initializes
the first cache_info->n_segs segments. A crafted image with
cache_info->n_segs smaller than the device count leaves the remaining
pcache_cache_segment structs zeroed (segment.data == NULL), and the
allocator can hand one to cache_kset_close(), which writes through the
returned segment's data pointer with no NULL check.

Bound the allocator's search to cache_info->n_segs so only initialized
segments are ever returned. A conforming cache sets n_segs equal to the
device segment count, so this rejects nothing legitimate.

## Which versions are affected by CVE-2026-80956?


## How do I fix CVE-2026-80956?

Apply the vendor's patch.

## Is CVE-2026-80956 being exploited?

There is no known exploitation of CVE-2026-80956 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80956 and fix it if it is affected.

What it is: CVE-2026-80956 is a 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-2026-80956 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-2026-80956/ (Markdown: https://insights.sbomify.com/CVE-2026-80956/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80956
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80956
- OSV: https://osv.dev/vulnerability/CVE-2026-80956

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80956/
Summaries are generated and may contain mistakes; the official description above is the record.