---
id: "CVE-2026-98906"
kind: "vulnerability"
aliases: ["CVE-2026-98906"]
title: "Linux kernel: failed lan966x MTU change leaves RX state inconsistent"
severity: "unknown"
cvss: null
epss: 0.00206
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["embedded", "lan966x", "linux-kernel", "networking", "package"]
not_affected_if: ["no-lan966x-hardware"]
published_at: "2026-10-23T12:18:24+00:00"
first_seen_at: "2026-10-23T21:57:33+00:00"
updated_at: "2026-10-25T12:38:50+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98906", "first_seen_at": "2026-10-23T21:57:33+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-98906", "first_seen_at": "2026-10-25T12:38:50+00:00"}]
---

# Linux kernel: failed lan966x MTU change leaves RX state inconsistent

When a Microchip lan966x network driver reload to a new MTU fails, the restore path keeps the new page geometry and XDP queue registration while reusing old RX pages. The sources do not describe an attacker-controlled exploit path, only a driver state inconsistency that can make the XDP path use a frame size larger than the restored pages.

_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 upstream commit 'net: lan966x: restore RX state on reload failure' (version unknown from the sources)

## Timeline

- 2026-10-23T21:57:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98906
- 2026-10-25T12:38:50+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-98906

## From the sources

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

net: lan966x: restore RX state on reload failure

lan966x_fdma_reload() backs up rx->page_pool and rx->fdma before
reallocating the RX resources for the new MTU. If the allocation fails,
the restore path puts these fields back before restarting RX.

However, the reload path also updates rx->page_order and rx->max_mtu
before calling lan966x_fdma_rx_alloc(). These fields are not restored on
failure, so RX can be restarted with the old pages, old FDMA state and
old page pool, but with the page geometry from the failed new MTU.

This can make the XDP path advertise a frame size derived from the new
page_order while the actual RX pages still come from the old allocation.
For example, after a failed reload to a jumbo MTU, xdp_init_buff() may be
called with a frame size larger than the restored RX pages.

lan966x_fdma_rx_alloc_page_pool() also registers the newly allocated page
pool with each port's XDP RXQ before fdma_alloc_coherent() is called. If
fdma_alloc_coherent() fails, the new page pool is destroyed, but the
rollback path does not restore the per-port XDP RXQ mem model
registration either.

Save and restore rx->page_order and rx->max_mtu, and restore the old page
pool registration for each port's XDP RXQ before RX is started again.
This keeps the restored RX state consistent after a failed reload.

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