---
id: "CVE-2026-98574"
kind: "vulnerability"
aliases: ["CVE-2026-98574"]
title: "Linux kernel bcmgenet: transmit after ring free causes use-after-free"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["bcmgenet", "infrastructure", "linux-kernel", "raspberry-pi", "self-hosted"]
not_affected_if: ["no-bcmgenet-hardware", "other-nic-drivers"]
published_at: "2026-10-18T16:17:09+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:23:11+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98574", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel bcmgenet: transmit after ring free causes use-after-free

In the bcmgenet Ethernet driver, the Tx queues are disabled before Tx NAPI is stopped during close-less paths such as Wake-on-LAN suspend, so a completion can wake the queue and a transmit can write to freed rings. The sources show a KASAN use-after-free write in bcmgenet_xmit on a Raspberry Pi CM4, which can corrupt kernel memory.

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

## How to check

- Run `uname -r` and compare against the fixed kernel in the sources, which the sources do not name
- Check whether the machine uses the bcmgenet driver (Raspberry Pi 4 or CM4) with `lsmod | grep bcmgenet` or `ethtool -i eth0`
- Check whether Wake-on-LAN is enabled with `ethtool eth0 | grep Wake`

## Fix

- Update the Linux kernel to a release that includes the upstream commit for 'net: bcmgenet: stop Tx NAPI before disabling the queues' (version unknown from sources)
- Until patched, unknown mitigation from sources

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98574

## From the sources

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

net: bcmgenet: stop Tx NAPI before disabling the queues

bcmgenet_netif_stop() and the Wake-on-LAN branch of bcmgenet_suspend()
both disable the Tx queues first and stop Tx NAPI several steps later. A
completion in flight calls netif_tx_wake_queue() in between, and nothing
stops the queue again, so a transmit can reach the rings after they have
been freed.

Close is safe because dev_deactivate_many() stops the qdisc first.
bcmgenet_suspend() does not, so stop Tx NAPI before the queues on both
paths.

KASAN on a Raspberry Pi CM4, driven from an MTU change because suspend
freezes user space before the callback runs:

  BUG: KASAN: use-after-free in bcmgenet_xmit+0x17f8/0x2258
  Write of size 8 at addr ffffff8055844a68 by task ksoftirqd/0/14
   bcmgenet_xmit+0x17f8/0x2258
   dev_hard_start_xmit+0x13c/0x588
   sch_direct_xmit+0x108/0x340
   __dev_queue_xmit+0x1190/0x3848

---

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