# CVE-2026-80584: s390/qeth: validate user buffer length in SNMP and ARP query ioctls

> A local attacker can exploit an integer underflow in the s390/qeth driver to trigger a buffer overflow, potentially leading to code execution or privilege escalation.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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-97691, BELL-CVE-2026-80584, DEBIAN-CVE-2026-80584, GHSA-cmjf-x265-ccvj, UBUNTU-CVE-2026-80584

## What is CVE-2026-80584?

CVE-2026-80584 is a high-severity 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/qeth: validate user buffer length in SNMP and ARP query ioctls

qeth_snmp_command() and qeth_l3_arp_query() allocate a buffer sized by
a user-supplied length (udata_len) without checking a lower bound, then
set udata_offset to a fixed non-zero value and pass both to a reply
callback. The callback bounds-checks the copy with

        if ((udata_len - udata_offset) < len)

Both fields are u32, so a udata_len smaller than udata_offset makes the
subtraction wrap and the check pass, and the following memcpy() writes
past the allocation. A udata_len of 0 also yields ZERO_SIZE_PTR from
kzalloc(), which the existing NULL check does not catch.

Reject buffers smaller than udata_offset before allocating, so the
callback subtraction can no longer underflow.

## Which versions are affected by CVE-2026-80584?


## How do I fix CVE-2026-80584?

Apply the vendor's patch.

## Is CVE-2026-80584 being exploited?

There is no known exploitation of CVE-2026-80584 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80584 and fix it if it is affected.

What it is: CVE-2026-80584 is a high-severity 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-2026-80584 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-2026-80584/ (Markdown: https://insights.sbomify.com/CVE-2026-80584/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80584
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80584
- OSV: https://osv.dev/vulnerability/CVE-2026-80584

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80584/
Summaries are generated and may contain mistakes; the official description above is the record.