CVE-2026-98239: Linux Vulnerability (CVSS 8.1)

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.

Metrics

CVSS 3.1

8.1/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.18%

6.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, < 0e52886c4324c9897c2c62f92be3dc8316cee67e; >= cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, < a58024835c704419bb46d2a34e5223f65605f958; >= cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, < 6fe5c3a2503983abb431d93faeadfc7f5e6a7e33; >= cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, < 5c216bfa9fb7b36804485e67975e9c98055b31ef; >= cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, < 161a403c8625e152de03d1da22bbf9cda6dc9f9f; >= cd6910501cfd9a3bdff2f5fc33c9f3cf165ca54a, < a9ce4053dc945c5372dedba5017ee675b30dc0c5
Linux	Linux	6.1

References

Timeline

Published: Oct 6, 2026
Last Modified: Oct 7, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-98239?

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.

How severe is CVE-2026-98239?

CVE-2026-98239 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 0.18% probability of exploitation in the next 30 days.

How do I fix CVE-2026-98239?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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