# CVE-2026-80550: s390/vfio_ccw: Fix out of bounds check on CCW array

> A local attacker can trigger an out-of-bounds read in the s390 vfio_ccw driver, potentially leaking kernel memory or causing a system crash.

- **Severity:** High 7.9 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:L`)
- **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:** 26 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-97713, BELL-CVE-2026-80550, DEBIAN-CVE-2026-80550, GHSA-fw9c-wxjq-5w67, UBUNTU-CVE-2026-80550

## What is CVE-2026-80550?

CVE-2026-80550 is a high-severity memory corruption vulnerability in Linux, published on 26 Aug 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:

s390/vfio_ccw: Fix out of bounds check on CCW array

The routine ccwchain_calc_length() counts the number of channel
command words (CCWs) that are chained together in a single channel
program, and rejects anything larger than CCWCHAIN_LEN_MAX (256) CCWs.

The loop itself is "do..while (count < 257)", and while the logic in
is_cpa_within_range() correctly adjusts between the 0-index array of
CCWs and the count of CCWs starting at 1, this means it would look
at a possible 257th CCW before ending the loop and (correctly)
returning an error.

Fix this by restructuring the loop to break as soon as 256 CCWs
(thus indexes 0-255) are examined, without looking at memory
outside the range.

## Which versions are affected by CVE-2026-80550?


## How do I fix CVE-2026-80550?

Apply the vendor's patch.

## Is CVE-2026-80550 being exploited?

There is no known exploitation of CVE-2026-80550 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80550 and fix it if it is affected.

What it is: CVE-2026-80550 is a high-severity memory corruption vulnerability in Linux, published on 26 Aug 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-2026-80550 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-2026-80550/ (Markdown: https://insights.sbomify.com/CVE-2026-80550/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80550
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80550
- OSV: https://osv.dev/vulnerability/CVE-2026-80550

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80550/
Summaries are generated and may contain mistakes; the official description above is the record.