---
id: "CVE-2026-98585"
kind: "vulnerability"
aliases: ["CVE-2026-98585"]
title: "Linux kernel fbnic driver: zero ring size handling in ethtool"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["fbnic", "infrastructure", "linux-kernel", "network-driver"]
not_affected_if: ["no-fbnic-hardware"]
published_at: "2026-10-18T16:17:11+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:22:57+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98585", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel fbnic driver: zero ring size handling in ethtool

A Linux kernel driver for Meta's fbnic network hardware passed zero ring sizes through ethtool to a rounding function that is undefined for zero. The fix leaves zero unchanged so the existing minimum-size check rejects it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Update to a Linux kernel release that includes the fbnic ring size fix (the sources do not name the version).

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98585

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

eth: fbnic: Avoid rounding zero ring sizes

roundup_pow_of_two() is undefined for zero. ethtool permits a zero ring
size to reach the driver, where the minimum-size check should reject it.

Leave zero unchanged while rounding nonzero ring sizes. The minimum-size
check then rejects zero deterministically without changing the established
behavior for other values.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_