CVE-2026-98239

/// Technical description

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

net: lan743x: fix RX checksum use-after-free

lan743x_rx_process_buffer() adds each non-first receive buffer to the

head skb's frag_list. On the last descriptor, lan743x_rx_trim_skb()

linearizes the head and frees the fragment skb metadata.

The checksum-success path then writes ip_summed through the local skb

pointer, which still points to the final fragment. This causes a

use-after-free write when a packet spans more than one receive buffer.

Set ip_summed on the surviving head skb instead. Multi-buffer receive

can occur after a live MTU increase because existing ring entries keep

their old buffer size until they are replenished.

A KUnit test invoking lan743x_rx_process_buffer() with a two-buffer

packet produced a one-byte KASAN use-after-free write before this change.

The same test passed after the change. The driver object also builds

with W=1. This was not tested on physical LAN743x hardware.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References