# CVE-2026-80961: dm-pcache: validate kset key_num and intra-segment bounds

> A local attacker with CAP_SYS_ADMIN can trigger an out-of-bounds read in the Linux kernel dm-pcache driver, leaking adjacent persistent memory to user space.

- **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-2026-80961, DEBIAN-CVE-2026-80961, GHSA-7hfq-329h-84pc, UBUNTU-CVE-2026-80961

## What is CVE-2026-80961?

CVE-2026-80961 is a high-severity 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: validate kset key_num and intra-segment bounds

Two more fields decoded from the cache device go unbounded. The kset
key_num drives cache_kset_crc() and the replay loop in cache_replay(),
the writeback worker and the GC worker, but only the magic and a
fixed-seed CRC are checked first, so a non-last kset whose key_num exceeds
the PCACHE_KSET_KEYS_MAX buffer reads past its end before the CRC compare.
A key's intra-segment offset and length in cache_key_decode() are taken
verbatim, so a key running past its segment is replayed into the cache
tree and the data CRC check and every later read hit then copy adjacent
persistent memory into the caller's bio -- an out-of-bounds read that
leaks to user space. Both fields are controlled by whoever supplies the
cache device (CAP_SYS_ADMIN); the CRC seed is public.

Add kset_onmedia_valid() to bound key_num before any kset read, and
reject a key whose offset plus length, computed in 64 bits, exceeds the
segment data_size. Valid metadata is unaffected.

## Which versions are affected by CVE-2026-80961?


## How do I fix CVE-2026-80961?

Apply the vendor's patch.

## Is CVE-2026-80961 being exploited?

There is no known exploitation of CVE-2026-80961 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80961 and fix it if it is affected.

What it is: CVE-2026-80961 is a high-severity 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-2026-80961 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-2026-80961/ (Markdown: https://insights.sbomify.com/CVE-2026-80961/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80961
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80961
- OSV: https://osv.dev/vulnerability/CVE-2026-80961

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80961/
Summaries are generated and may contain mistakes; the official description above is the record.